growing chestnuts

Over the past eight years we have attempted to help chestnut growers establish a commercial chestnut industry in Michigan and other Midwest states. In 1992, we found a fledging chestnut industry in Michigan struggling to establish and maintain young chestnut orchards based mostly on the Chinese chestnut tree. For several reasons, these early attempts were frought with failure and many growers were losing time, money, and ultimately interest. If we had to determine the one main reason why establishing a commercial industry was so difficult in those early years it might be said that the growers’ only level of knowledge was based on a few pre-established plantings located in other environs and maintained by hobbyists or people willing to accept any level of production without regard to cost or payback. This document is written for those interested in establishing commercial orchards where cost and profit are motivating factors.

Among other criteria, you can "call" yourself a true commercial nut producer when you become as concerned with revenue flow as with nut production. You may "call" yourself a commercial nut orchardist if you are willing to spend $20,000 establishing an orchard that will provide you with $2,000 of annual revenue, but in reality you are really just an "orchard subsidizer." If you only spend $1,000 establishing a chestnut orchard, then you are a hobbyist. If you are ill-prepared to spend the appropriate amount of money required for good chestnut tree varieties and other important yet expensive facets of orchard establishment, then you aren’t really a commercial orchardist, either. Obviously, as with other business ventures you must be willing to spend money to make it, but you also must be frugal due the agricultural climate in which we find ourselves in today. Applying water, nitrogen, herbicides and pesticides to trees that give less than an optimum return is not only a business loss, but also a detriment to our environment.

One of the objectives of this document, as stated above, is to provide you with help for informed decision making. One of the first questions posed to me in 1992 was a simple question, “How long before the trees start producing nuts?” You didn’t need to know this information if you were a backyard or hobby orchardist, as any nuts in any time frame would be fine. However, it was one of the critical questions that needed to be answered before commercial growers should invest in chestnuts. Now in 2001, this one question still haunts me. That single question required more knowledge and information than any article, book, document, individual expert or nut-growing group could provide. By posing that one question, we knew that we understood very little about the first step in forming a commercial chestnut industry.

To answer that question we need to know the type of chestnut tree, the age of the tree when planted, how the tree was treated after planting, and how fast it would grow and mature. Even armed with that information, we would still be guessing for very few of us in Michigan have produced commercial quantities of chestnuts even though many have been trying for twenty years. My standard answer for that question is still “within 6 years.” That answer is based on my attempts to reconcile the large number of different chestnut types that have been planted and the different conditions to which they were planted. If you read through this document, you will find that I can now state explicitly that chestnut trees can produce within four years, but that is predicated on a set of specific conditions such as the variety, the pollination source, whether deer, irrigation and weed controls were applied, etc. I mention this to ensure you that there are no easy answers but as time goes on and if interest remains high, all of us will find answers together.

Michigan State University has always maintained some interest in chestnut production. Dr. Lee Taylor established a planting of chestnuts on the horticulture farm in the early 1970’s. Our laboratory started working with chestnut blight and the American chestnut tree in the early 1980’s, but, we did not become interested in cultivation and nut production until the early 1990’s. About that time, the Midwest Nut Producers Council and the Michigan Nut Growers Association established the Nut Variety Trial at Michigan State University’s Southwest Michigan Research and Extension Center (SWMREC) in Benton Harbor. While the trees planted at SWMREC were becoming established, I turned to 16, twenty-years old Chinese chestnut trees from Connecticut that Dr. Taylor had planted on the MSU Horticulture farm. We started collecting yield data on these 16 trees and after three years it was evident that each tree produced different amounts of nuts each year and at least two never produced nuts. One year, tree #1 produced the most and the next year tree #4 produced the most and tree #1 barely had a nut. The next year tree #1 and #4 produced average yields of small chestnuts and tree #16 which hadn’t produced much the previous two years, produced the most chestnuts although they were small. It became obvious that in any single year, less than half of the trees were producing any nuts at all, and these trees were over twenty-years old! Then, two of the trees looked like they were going to die as the leaves were sparse and small. We proceeded to prune, water and fertilize the trees (something that hadn’t been done for years) afterwhich they recovered and began producing small nuts again.

I bring up this case of the 16 MSU horticulture trees because I believe what I was seeing was the future of the Michigan chestnut industry if things were not changed. Those trees planted on the MSU Horticulture farm in East Lansing were trees planted from nuts dropped by a mother tree called ‘Sleeping Giant’ from the Connecticut Agricultural Experiment Station in New Haven, Connecticut. This tree in Connecticut has been described as a good variety with many fine attributes. But, what we got were nuts carrying only 50 percent of the ‘Sleeping Giant’ tree and 50 percent of other trees in their orchard. Each nut would have different genetics much like the children of a family; none would be exactly like either parent tree and none of the trees in the orchard would be like any of the other trees in the orchard.

When Michigan chestnut hobbyists planted nuts to start their trees, it didn’t matter too much to them what characteristics the trees had, in fact, sometimes the more absurd the characteristics the more interesting the tree. However, a commercial industry can not become established on seedlings. Uniformity and predictablity are requirements within an orchard. Dealing with the environment and its interactions with biological entities is hard enough without employing as many tools for predicability as possible. In the orchard, this uniformity is achieved with grafted or budded varieties. There are literally thousands of chestnut varieties found around the world but few are available in commercial numbers in this country. The chestnut variety trial at SWMREC, provided the commercial chestnut orchardist their first opportunity to observe and compare chestnut varieties growing side by side at one location in the Midwest.

These, trees established in 1992, went through the coldest Michigan winter in recent history after their second growing season and some were lost. But, those losses were the start of chestnut variety data and by 1995, we were on our way to developing guidelines based on the reactions of different chestnut varieties growing at one location in Michigan. Since then, the Northwest Horticulture Research Station near Traverse City has become the second home for a public chestnut variety trial to help growers in that location compare variety performance.

The Midwest Nut Producers Council has divided up the focus of chestnut research into three overlapping areas. The first deals with germplasm, the second deals with the horticultural aspects of growing good trees for good nut production, and the third deals with harvest, post-harvest treatment and marketing. All of these are interrelated and each feeds back information to the other. For example, if we find consumers are more interested in one type of chestnut than another, then that information would alter the germplasm aspects of chestnut production as well as marketing. If one type of chestnut stores better than another then that will alter marketing as well as germplasm aspects. The nut tree variety trials were established to study the germplasm aspects of chestnuts; experimental plots and growers' farms currently help us learn how to horticulturally manage the trees and we are now beginning to focus on post-harvest and marketing issues. Soon we will have a three-ring circus of experiments, trials and data! But right now those data is sparse.

We suggest that you join a growers’ group so that you can find people with interests similar to your own in terms of growing chestnut trees. You’ll see below that some of these groups are mainly for hobbyists and others are for commercial growers; and many growers are members of both groups. If your goals are to be a commercial grower, you cannot follow some of the recommendations that a hobby organization may suggest. If you have questions, call your county extension agent or contact Dennis Fulbright at fulbrig1@msu.edu.

Chapter 1: Germplasm

1.1 Overview

There are several species of chestnut trees that are native to three continents and each species shares common characteristics with the others yet has its own unique characteristics and qualities. All chestnuts are deciduous and have alternate, parallel-ribbed, conspicuously toothed leaves. The leaves are always oblong or oval in shape but leaf size and shape will vary from species to species. All species are monoecious, that is, male and female flowers are both borne on the same plant, but most plants are self-sterile, that is the pollen on one tree or variety will not pollenate itself or the same variety. This sterility is thought to be due to genetic interactions between the pollen and ovary. This is not an issue in a chestnut forest where each tree is an individual and can pollinate its closest neighbor. However, in a chestnut orchard established using grafted varieties at least two different varieties are needed, variety 1 to pollen variety 2 and vice versa. Some varieties are male sterile, that is, in the process of creating the variety, the plant lost the ability to produce pollen. In this case if variety 1 is pollen sterile, then it cannot pollinate variety 2 even through variety 2 should still be able to pollinate variety 1. To pollinate variety 2, variety 3 needs to be added to the orchard. I bring this up now to prepare you for some of the complexities that will be covered in other sections and chapters.

In the Midwest, chestnuts flower in late June and July. This doesn’t always prevent frost damage as flower buds can be damaged during late spring frosts. The showy chestnut “flowers” are made up of yellow pollen-bearing catkins (male) which are borne from the leaf axiles of the current year’s shoots. When this flowering first begins, usually within the first 12 years, only the male flowers will be produced. Female flower production will follow one to several years later. The female flower which is small and can be easily overlooked, appear at the base of the male catkins. The female flower will begin to enlarge and swallow up the catkin as it enlarges into the infamous brickly bur that will ultimately house the chestnuts. Flowers that are not pollinated may continue to enlarge as if they have been pollinated.

See Catkin, Flower, Bur Photos

The nuts themselves inside the bur begin enlarging late in the season. If a flower was not pollinated and the bur enlarges and stays on the tree through the summer and fall, it will yield flat crescent-shaped brown shells without nut meat inside the shell. This can be confusing for those who have never seen a chestnut since the shells are inside the bur. But if you tried to open this flat nut, the few morsels of nut membrane would not satisfy even the most nondiscriminating squirrel. If pollinated, the nuts enlarge and ripen in mid- to late-September and most are ready for harvest in late September through mid-October.

Pollinated and Unpollinated Chestnut Photos

1.2 Chestnut Seedlings or Grafted Varieties: What Are the Differences?

I still see ads and still hear of growers establishing chestnut orchards with “seedling” chestnuts. This is such a waste! Would you establish a cherry, peach, or apple orchard by dropping a pit or seed into the ground and waiting for the tree to grow? Maybe 100 years ago. Today, all commercial fruit and nut tree orchards are established with varieties that have been selected by experts for various traits. These varieties are not produced through seed, but are cloned or grafted onto the stems of seedlings that will support the variety chosen. In this manner, a single tree can be copied millions of times by simply cutting small branches from the choosen tree and attaching it onto the stem of established seedlings or large mature trees. The branch that is cut from the chosen tree is called the scion wood and the tree that it is attached to is called the rootstock. The rootstock may be from a seed that was dropped in the ground or it could be a large mature tree that was never grafted or grafted to a variety that does not have the traits which you wish to have in your orchard.

How rootstock is choosen and mass produced may be important but not something we wish to discuss at this point in time. What we wish to impress upon you is that the term “variety” is almost always reserved for genetic material with certain identifiable features or traits that can be copied or cloned by grafting to produce identical copies. Probably the most well known story is the ‘Naval’ orange. A mutation from a seed bearing orange, the ‘Naval’ orange did not produce seed. The scion from the ‘Naval’ was grafted to rootstock and sent to California where the original grafted tree supporting the original scion can still be viewed (called the Washington ‘Naval’ orange tree).

There are several ways to attach scion wood to rootstocks and some methods may work better than others for different tree species or under different conditions. For example, budding is a type of grafting where just the bud from the chosen tree is placed within the bark of the rootstock. The scion in this case would be the bud. Chestnuts are commonly grafted with scion branches or with buds, but in either case, the scion will produce trees identical to each other. Once the scion has sprouted and produced substantial growth, the rootstock above the point of scion attachment will be removed so the scion becomes the only growing material above the point of scion attachment.

If you are following the ideas presented so far, then you will realize that the rootstock to which the scion is attached will be produced by planting seeds and one rootstock will necessarily be genetically different from any other rootstock. Therefore, even if the scion is the same throughout the orchard, the rootstock will be genetically distinct from tree to tree. This is one reason why trees planted in an orchard still show some variability. The genetic diversity of the rootstock can be ignored in many situations, but there have been several cases where rootstock variation has lead to problems as minimal as bark discoloration or as serious as graft failure and early tree death. In plant systems that have been studied for several decades, the knowledge of rootstock and scion wood combinations can lead to important orchard management opportunities such as rootstock that can lead to the preferential dwarfing of scion growth or resistance to soil borne root diseases.

We are far away from that level of genetic management in chestnut, but we do believe that fewer problems will develop when the rootstock and scion wood are genetically related. If this theory holds true, then Chinese chestnut varieties should not be grafted to American chestnut and vice versa. That does not mean you can’t do it or shouldn’t try it in experimental situations, but it does mean that unless further research points a new direction, commercial orchards should be established with trees produced by closely related rootstock and scion wood.

1.3 Chestnut Varieties

There are three important species of chestnut that contribute to chestnut orchard varieties. But before we discuss those species, lets briefly discuss the species that may, someday, contribute specific genes to new variesties, but right now are not the foundation for good orchard varieties.

First, there is the native American chestnut (Castanea dentata). A spectacular forest tree until the accidental introduction of the chestnut blight fungus that destroyed the Eastern chestnut forest during the first fifty years of the 20th century. As the basis of an orchard industry, this species has two strikes against it at the outset. It is chestnut blight susceptible and it produces nuts that are too small for anything but squirrel food and processing. Blight resistant trees are on the horizon for the early part of the 21st century but the trees would still have to be bred for nut size. No varieties exist today based on the American chestnut and few ever existed since this tree was so common and the forest so vast that if anyone wanted an American chestnut they would only have to wander in the woods in the fall.

One chestnut variety called ‘Paragon’ which probably has American chestnut in it, could be found in some orchards planted when blight first struck the North American continent, but the blight fungus destroyed these farms as it destroyed the chestnut forest. American chestnuts are very sweet and they have a certain nostalgic appeal to the public, but unless a specific market is developed, at 80 to 120 nuts per pound, these nuts are probably too small to attract much business.

The second variety is the chinkapin chestnut or Ozark chinkapin (Castenea pumilia). This too is blight susceptible and only produces one nut per bur. But the size of the tree is probably its biggest drawback as it only grows to shrub size. Someday, the genes for this dwarfing may be important in bringing about smaller trees in chestnut orchards. Other genes may also be used in breeding better orchard chestnuts such as insect and disease resistance, but currently this species, along with the American species should be avoided in commercial orchards.

The species for which varieties have been selected are those that have a long history of chestnut cultivation, including the Chinese chestnut, the Japanese chestnut and the European chestnut (Castanea mollissima, C. crenata, and C. sativa, respectively). Some of the varieties actually represent hybrids or crosses among these three species. The species are similar looking at first, but using differences such as tree size, leaf shape and nut characteristics, one can soon begin to tell them apart. The hybrids are another story. It may be very difficult to tell what species make up the hybrids. In fact, in most of my dealings when trying to determine species by looking at bark, stem and leaf samples mailed to the laboratory, I simply say “American-like” or “other than American-like.”

In Europe and China there are literally hundreds of varieties that span the ages of civilization. At the Second International Chestnut Meeting in Bordeaux, France held in 1998, I was surprised by the large number of chestnut varieties that France grows. Then you can add in Italy, Spain and Turkey and you have not even begun counting them in Japan, China and Korea; the number of varieties are enormous. Because of plant quarantine restrictions, we have only a few of the European and Chinese varieties available. Of those varieties that are availbale in their country, scientific information is lacking on the characteristics of these trees and nuts.

It was precisely for this reason that the Nut Tree Variety Trial at the Southwest Michigan Research and Extension Center in Benton Harbor was planted. For the first time orchardists could see the diffferent varieties and compare their performance in one area. Performance data have been published yearly in SWMREC’s Annual Report. SWMREC has several of the varieties planted but they represent only a few of the dozens of varieties available in the states. Many of these varieties have just now become available as growers have insisted on planting varieties instead of seedlings. The varieties that can be found at SWMREC and the Horticultural Research Station near Traverse City do not represent all commercially available varieties, but certainly represent a large percentage of them.

Dr. Sandra Anagnostakis has collected some information on most of the varieties that are available in the United States and recently published that information in the 90th Annual Report of the Northern Nut Growers Association (1999). Most of the information that is included in the report is clearly subjective and unsubstantiated, but the information, if taken for what it is worth, is a good start on chestnut variety descriptions. It must be remembered that a variety is only as good as the source of the scion wood and each variety will perform differentially in different regions of the country. A variety trial in a location near your farm is the only way to predict how a variety may fair in your area.

I have included portions of Dr. Anagnostakis’s report (see PDF document) within the appendix of this report. I have also updated it in regard to variety performance in Michigan variety trials.

1.4 Important Varietal Characteristics

We know that orchardists want trees that produce large yields of high quality chestnuts. But we really have few ideas regarding what the consumer wants in chestnut since a large chestnut market with a discriminating consumer base has not yet been established in North America. We have some information based on Italian imports and the nuts that have gone to market from a few established commercial orchards.

Until we have marketing reports regarding the preferences of the consumer, we can only provide what we think the consumer wants and what we are able to grow. What are the attributes that a orchardist wants in a chestnut tree? As mentioned earlier they should want large yields of high quality nuts. But they should also want consistency, that is, a variety that performs the same way year in and year out regardless of environmental conditions. Varieties that respond less to extremes of the environment are much more valuable to the orchardardist than varieties that alter their physiology to external stimuli. If a variety experiences a hot dry summer or a wet cool summer, an orchardist wants the variety to produce the same large yields of high quality nuts each year. So the primary attribute that leads to a good variety is consistency. Yet, when growers find a potential seedling tree with some high quality attributes, they are usually surprised when I show a lack of interest. If you tell me that the attributes you find pleasing have appeared 9 out of the last 10 years, I’ll be listening.

Since we are discussing important traits like consistency, let’s look at some other attributes of an ideal chestnut variety. It would fight insect pests and disease organisms; grow fast so as to grow above deer browse as quickly as possible; produce male and female flowers and burs within the first four years; be pollen fertile so that it could pollinate other varieties in the orchard; produce nuts of an expected size each year regardless of the type of weather the tree experienced; grow to a robust size, but not so large as to rise above the equipment used to manage the orchard; ripen and drop nuts at the same time each year; and, produce high yields of quality nuts each year.

Of course, there is no single variety that can do it all so we must pick and choose varieties that come as close to perfection as possible in each catagory—sort of like a decathelon champion. Since we have little experience with many different varieties we thought it would be important to set a standard by which all other varieties could be judged. That variety has been and continues to be the Japanese X European hybrid out of California, ‘Colossal’. This variety is sold by at least four different nurseries and it is the preferred variety of the Western Chestnut Growers. Each year Fowler Nurseries of Newcastle, California buds and sells thousands of ‘Colossal’. As discussed in section 1.8, below, ‘Colossal’ has continued to be the yield leader at SWMREC, but ‘Colossal’ has two flaws that will ultimately be its downfall in the Midwest. First, it is chestnut blight susceptible and it cannot be grown in places where chestnut blight is found. In California, chestnut blight is rare and will not be a problem for many years, if ever. In Michigan, chestnut blight is present in American chestnut plantings and we have seen chestnut blight on first year ‘Colossal’ trees when we intentionally planted it next to blighted American chestnut trees. It was hoped, early on, that ‘Colossal’ might have some level of resistance to chestnut blight as frequently seen in other Asian species of chestnut. But this does not seem to be the case.

The second problen faced by ‘Colossal’ growers is the difficulty in removing the shell and pellicle, the paper membrane between the shell and the nut meat. The invaginations associated with the kernal appears to hold the pellicle to the surface of the nut meat which makes it difficult to remove on some nuts. This may not be a problem if shelling equipment is developed that can remove both the shell and the pellicle. At the same time, we found that chefs in many of Michigan’s best restaurants who used ‘Colossal’ chestnuts in their recipes were able to remove the shell and pellicle with little effort.

As stated, technology can help with pellicle removal but it cannot help with chestnut blight. Those orchardists planting ‘Colossal’ must be on the lookout for chestnut blight in order to remove it before it spreads to other trees. If sources of blight are far away and there is little movement of plant material from blight-infested areas, a chestnut orchard in isolated locations of Michigan may stay uninfected for years. We have seen American chestnut trees (most susceptible to blight) in Michigan live for in the face of chestnut blight without becoming infected. Still, chestnut blight resistance is something we want to move toward in the future.

Colossal Inoculated with Chestnut Blight

If ‘Colossal’ harbors these two negative traits why does it stay as a standard and as such a popular tree to plant? ‘Colossal’ produces the largest yield and sooner after planting than any other variety at SWMREC. As soon as another variety can match or beat ‘Colossal’, it should be considered for planting, but so far, few come close. The nuts produced by ‘Colossal’ are very large and this is still thought to be one of the important aspects of consumer preference. If you need a pound of chestnuts for a recipe, it means dealing with 18-25 ‘Colossal’ nuts or 30-50 nuts of another variety. Again, as soon another variety can match or beat this standard, it should be cautiously embraced by orchardists.

Are there varieties that can match ‘Colossal’? We are constantly planting old and new varieties into the two Michigan variety trials attempting to find trees that will beat the standard. Claims will be made, but until they go head to head in a public-supported variety trial in your area, be cautious and skeptical.

1.5 Breeding New Varieties

The largest chestnut breeding program ever attempted in this country is currently underway in Meadowview, Virginia. The goal of the breeding program of the Amercan Chestnut Foundation is to breed blight resistance into the American chestnut tree and release the blight-resistant variant back into the Appalachian Mountains. While there may be some indirect benefit to orchard chestnuts in time, no new orchard varieties are expected to be produced from this program. If a chestnut industry does get established in the USA, then the information garnered from this breeding program will definitely be put to good use breeding high quality chestnut trees for orchards. In the meantime, we have dozens of potentially high quality chestnut varieties to screen and use in the orchards until such time as a breeding program is initiated.

1.6 What Varieties Should I Plant in My Chestnut Orchard?

Opinion is going to vary when answering this question—and it should! Experiences are going to be different in different parts of the country and world. But it should be based in sound, fair, comparisons where the “playing field has been leveled” in as many criteria as possible. I still hear people saying that one variety is better than another variety, yet they have never seen them both grown at the same location. In Michigan, I think the variety known as ‘Colossal’ should be given strong consideration for inclusion in most orchards (see next sections for results of Michigan’s varietal trials). Growing a grafted chestnut tree which is a “variety” requires a pollinator tree to be grown due to the necessity for chestnut to be cross pollinated. This means the orchard will need to have two varieties. The pollinator does not have to be dedicated to pollination—it can be a good chestnut producer itself. Fowler Nurseries, one of the nurseries that sells ‘Colossal’ in California recommends the variety ‘Okei’ as a pollinator for ‘Colossal’. Previously, they recommended the variety ‘Nevada’ to pollinate ‘Colossal’ but ‘Nevada’ is a poor nut bearing tree and has died off in some of the colder areas in Michigan and it is our hope that we can wean-off of ‘Nevada’ in the near future. We have also experienced winter kill in Okei and we need to keep searching for good pollinators. Pollination has not been studied in Michigan variety trials and we assume that varieties other than ‘Okei’ and ‘Nevada’ will pollinate ‘Colossal’. In our variety trials, so many different varieties are planted in close proximity to each other that we have no idea who is pollinating whom.

In most situations, two varieties in a chestnut orchard could be the limit, but unfortunately, another weakness of ‘Colossal’ is that it is male sterile; its catkins fall off early since no pollen is generated. Without pollen, ‘Colossal’ will not be able to pollinate its own pollintor. Therefore, ‘Okei’ , ‘Nevada’ or whatever tree was planted to pollinate ‘Colossal’ will not be pollinated. If this is ‘Nevada’, there is no great loss as the nuts of ‘Nevada’ in Michigan are not worth harvesting. However, if the planted pollinator was to be ‘Okei’, then this would be a great loss because the nuts of ‘Okei’ are commercially acceptable. Therefore, to pollinate ‘Okei’ or another pollinator means that you need a third variety in the orchard. Whether or not this third variety is likely to pollinate ‘Colossal’ would depend on the variety and on further research. At this juncture, you need at least three varieties, therefore, a fourth and fifth variety should also be considered since you really don’t know yet what the best varieties are for your area. Let’s stop here and assess this variety issue.

Varieties in well established fruit and nut commodities are chosen for several reasons; one reason usually predominates. Sometimes consumer demand plays a primary role in what variety is chosen. Sometimes a variety is chosen because it ripens early and the first to market has the most to gain. Sometimes a variety is chosen because it ships or stores well. And, yes, many times a variety is chosen because it yields the best. Varieties are also the subject of many “farm legends” where one variety is rated better than another by the growers without evidence to support such claims. This is one reason land grant universities and the USDA/Cooperative Extension Service has spent so much time over the years developing variety trials.

The real question is what do you want to do with your chestnuts? Do you want to be early to market? Do you want to be late so the chestnuts are fresh for the holidays? Do you want to grow chestnuts for a niche market, like organic chestnuts or chestnut flour? Do you want to grow what everyone else is growing so you’re sure to have a market? Do you want to sell to specialized chestnut markets, farm markets or to retail stores? We can’t tell you that we have a single chestnut for all these situations nor can we tell you that there is a specialized variety for each of these situations. I will go out on a limb and tell you that if we are successful with a chestnut program, someday, there will be chestnut varieties to fill all of those markets.

Until then, the main reason to grow ‘Colossal’ at this time is that it is the best yielding tree, the fastest growing tree, produces the largest nut and is commercially available in large supplies. We know what to expect of ‘Colossal’ and we know how it will grow and respond. We don’t know much about other varieties at this time.

So into our orchard goes ‘Colossal’ and ‘Okei’ (or ‘Nevada’ if we can’t get ‘Okei’). Why wouldn’t we leave it like that? We wouldn’t want to leave it like that because ‘Okei’ would not be pollinated. But there is another reason and that reason is more important than pollination—it’s diversity. Chestnut blight or another unknown or new pest, could arrive and ravage your trees if you only have one or two varieties and especially if those varieties are primarily based on the same species (C. sativa, C. crenata or C. mollissema). Planting more than one variety may give you insurance against the hazards that nature has always thrown against farmers, sooner or later.

With chestnut, we have a great weapon against such potential disasters. Our varieties can be selected from three or more different species and their hybrids and unless you are an expert in chestnuts, the nut doesn’t change that much. In most fruit and nut industries, the germplasm is so genetically narrow that growers are in constant danger of a new pest wiping out all of the germplasm in a field or orchard. In a chestnut planting with appropriate diversity, the pest would have to eat and reproduce on varieties associated with Chinese germplasm, Japanese germplasm, European germplasm (and maybe Korean germplasm if it is truly a distinct species), and their hybrids. We need to learn how to exploit these varieties in our orchards without losing yield or quality. We need good varieties in all of these species and we need to get them into the orchard—now.

A new variety ‘Qing’ that is beginning to be pushed hard by nurseries is one that we have yet to generate any data. It was discovered as a single tree in Ohio and is now being sold by some nurseries. I have seen a few nuts from this variety and they seemed outstanding. But will this variety produce 50 pounds of nuts within 10 years in southern or northern Michigan? The 'Qing' tree that people are talking about right now is a large mature tree, several decades old. Will the grafted 'Qing' trees now being sold by nurseries measure up to parent trees? We need to watch and determine just how cold tolerant it is. Would it be alright if it doesn’t produce 50 pounds of nuts within 10 years? Probably, as long as it has other strong attributes and helps bring about orchard diversity. Let’s hope that ‘Qing’ or another variety is ready to best our current standard ‘Colossal’.

1.7 Variety Performance at SWMREC, Benton Harbor, Michigan—2000

See Yield Table

See Graph

See SWMREC annual report

1.8 The Role of Nurseries

No organization will contribute more to the commercial chestnut industry’s success or failure as that of the nursery industry. Most of us will not (or should not) graft our own trees as it takes time away from other important aspects of orchard management. Nurseries must strive to provide the best varieties at resonable cost so that chestnut orchardists have a chance to establish these varieties in their orchards. If nurseries sell mediocre varieties just because they are available, easy to graft or have name recognition they are doing a disservice to the future of the chestnut industry. There are few reasons for nurseries to propagate antique varieties unless those varieties have traits important to the producers’ needs. One of our problems has been determining the producer’s needs, but one need for certain is the need to make enough money to stay commercial.

Good nurseries have the expertise to produce thousands of healthy trees and should be able to maximize the number of grafted trees while absorping the losses for grafts that refuse to grow. Life in and out of the orchard is busy enough for most of us. A good motto to follow is, let the nurseries do what they are best prepared to do. Although, it may not seem like it at the time you pay your bill, the cheapest part of orchard establishment is buying high quality varieties. The cost of the trees distributed through the life of the orchard ultimatetly will be negligible.

For large, well-established orchard industries like cherry or apple, a grafted tree will cost less than $10 depending on its size (usually judged by diameter—5/8 inch, for example) and the number you order. New varieties that have a lot of demand and sell out quickly may cost more. There are few nurseries that service the chestnut grower and because of this and other reasons, such as high demand for the few trees available, grafted chestnut varieties will cost a little more. Grafted trees should cost between $10—$15 plus shipping and handling (storage). Again, the number of trees ordered and the size of the tree will also be important in the final cost.

Nurseries may sell chestnut seed and seedlings. Unless you plan to graft your own trees, or unless you wish to look for new varieties among all that genetic variation, do not even consider buying seedlings to establish a commercial orchard. None of the seedlings will breed true even if they are from selected mother trees such as ‘Colossal’ seedlings or ‘Sleeping Giant’ seedlings—you might as well invest in race horses where the genetics are better understood. Growing seedlings should be saved for the hobbyist or the most scientific aspects of a research program where breeders will search for new and useful traits. Seedlings are not part of any commercial orchard industry. Seedling orchards remain one of the problems that plagues older chestnut orchards throughout the Midwest.

Specialist at the nurseries normally should be able to tell you about the variety you need to plant for your area. But they are also in business and will sell you what you want to buy. Therefore, you need to do your homework before you submit your order. They may or may not remind you that you need a polIinator for the variety you ordered and you should be able to tell them that you have enough pollinators already or ask them what they think is the best pollinator for the variety you just ordered. Of course, our problem still remains that we do not always have scientifically-based answers for these situations, and we can only tell you what has worked in the past under specific circumstances. This and so many other unknowns, after all, is what makes this a pioneering effort.

Nurseries may suggest varieties that are new to you or varieties that you have not had to opportunity to compare to other varieties in a variety trial. Sometimes nurseries sell varieties that are being “promoted” because the variety has done well in their area and they truly believe it will do well in your area. At this point you have about four choices, 1) do what the nursery suggests; 2) call your extension agent and ask them their opinion; 3) call someone from the Midwest Nut Producers Council; 4) buy a few to check them out for yourself. Remember, sometimes these varieties are being promoted because it gives the nursery a reputation for offering something that another nursery does not have and sometimes they may be out of other varieties and this is the only variety left.

Where to Obtain Grafted Chestnut Trees (updated January 2002)

Below you will find nurseries servicing the chestnut industry. Most of the statements are taken verbatim from their web pages. You must go to the web pages to see the price per tree and the sizes that are sold. Also, many selections may be sold out for the current season and this is usually noted on the web page. If you are a Michigan chestnut grower, it is suggested that you go to the varieties section below to see what varieties have done well. One nurseryman below states that it takes 12 years for ‘Colossal’ to mature. It is not known what that statement means as maturity usually means the production of female flowers and most ‘Colossal’ will be producing female flowers and nuts in their third growing season after planting.

Please remember, several potential varieties sold in these nurseries have not been planted in variety trials in Michigan and other chestnut growing areas. It is our suggestion that you not accept, as fact, data that have not been confirmed in public variety trials in your area. That is not to say that the claims presented are false, its just that environmental and climatological aspects of each location may alter traits and characteristics of trees.

No matter what else you learn, please follow John Brittain of Nolin River Nursery’s advice when discussing the benefits of grafted varieties when compared to seedling trees. He says, “Seedling trees, in contrast, almost always differ from the parent tree from which the nuts were collected and planted, and in comparison with a grafted parent tree, will usually be less desirable in some respects. Furthermore, seedling trees must grow through a juvenile period before they are capable of flowering and nut production.”

While you will pay more for a grafted tree, we know from our Colossal plantings in Michigan that each tree can pay you back within 5 years.

Fowler Nursery
525 Fowler Rd.
Newcastle, CA 95658
Phone: 800-675-6075

Sells ‘Colossal’, ‘Nevada’, ‘Okei’, ‘Silverleaf’, and ‘Linden’
Prices are based on size and generally from $8.00 to $12.00 per grafted tree. They only will deal with orders greater than 100 trees as of 2001.

Englands Orchard and Nursery
316 S.R. 2004
McKee, KY 40447-9616
Phone: 606-965-2228 or 606-965-2270
Email: nuttrees@prtcnet.org
Owner: Clifford D. England
http://www.nuttrees.net/nuts.html

Specializing in exotic fruit and nut trees for alternative crops chestnuts, hazelnuts, pecan, black and English Walnuts, heartnuts, rootstock and much more. They grow several of the Chestnut Hill cultivars (Dunstans). They report that the Dunstan cultivars that are the most promising are Alachua, Carolina, Willamette and Carpenter. They also sell Colossal.

‘Qing’ - Chinese selection, Very sweet nuts, Pellicle separates freely from nut, 2 to 4 nuts per bur; nuts are a light mahogany in color. Qing has no sign of chestnuts blight. Original tree planted in 1938 and to date tree is 108 inches in diameter and 35 feet tall. An excellent commercial nut due to its taste, size and keeping qualities. 18 to 22 nut per Lb.

‘Yoder # 2’ - Chinese chestnut selection, Pollinator for the original Qing chestnut tree. Taste similar to Qing, well filled nuts, Mahogany in color, pellicle separates freely, Separate from burs. Nuts store very well. Tree is 118 inches in girth, 35 to 45 ft. tall. 26 to 30 nuts per Lb.

‘Jack’s’ - Chinese selection, Produces annual heavy crops of large dark-red nuts. Tree is somewhat dwarfing at aprox. 25-year-old tree is only 20 feet tall with a spread of 20 to 25 feet. Most of its growth is reserved for nut production. 20 to 23 nuts per Lb.

‘Eaton’ – C X (J x A) hybrid, a seedling of Sleeping Giant, Flavor, texture, and sweetness are among the best, ripens 3 to 7 days earlier than most Chinese. 30 to 40 nuts per Lb.,

‘Crane’ - Chinese chestnut selection from the Chekiang province of China. Nuts are dark-red to brown in color; Flavor and keeping qualities are excellent. Crane is best adapted to the middle and southern USA. Produces a large tasty nut in this region. 26 to 32 nuts per Lb.

‘Colossal’ - E. x J. hybrid Tree is pollen sterile. Produces very large nuts and is known as the number one commercial variety. Trees mature at 12 years old. 18 to 20 nuts per Lb.

‘Carolina’- C x A, Dunstan hybrid Patent # 7041. Nuts are dark brown and a good commercial cropper. 24 to 28 nuts per Lb.

‘Willamette’ - C.x A. hybrid, Dunstan hybrid patented; Reliable producer of tasty large nuts grows well in zone 5b. 18 to 22 nuts per Lb.,

‘Carpenter’ - C x A hybrid, Dunstan hybrid Patented, very vigorous with upright growth habits, best for the southeast. 20 to 25 nuts per Lb.

‘Castanea Henryi’ - Chinese timber chinquapin / Imported from China (not hybrids) 1 yr. Old seedling. Castanea H. is a large American chestnut timber type tree. Gall Wasp resistant and immune to chestnut blight. Reportedly cold hardy to zone 5.

Burnt Ridge Nursery
Phone:360-985-2873
burntridge@myhone.net
http://landru.i-link-2.net/burntridge/

Burnt Ridge Nursery & Orchards, Inc. is a family owned farm, in business since 1980. Our 20 acre farm is located in the foothills of the Cascade mountains with a beautiful view of Mount St. Helens. Our mail order nursery specializes in disease resistant bushes & trees that provide edible fruits or nuts. We also have a large selection of N.W. native plants. We send nice sized, healthy, well-rooted plant material. The varieties we carry have done well in our orchards. If you have any questions, please feel free to call or write. We can help you make appropriate choices for your growing area. Michael & Carolyn Dolan

CHESTNUT TREES

Grafted onto their own seedlings under controlled pollination conditions to insure long-term graft compatibility.

‘COLOSSAL’ - (Japanese x European) Parent tree produces exceptionally big nuts of good quality. Early ripening, easy peeling, popular orchard variety. Grafted seedlings, or Layered (own roots). Available in sizes and prices as listed above, and also as 10-12 ft., 1 1/2" caliper trees at nursery only.

‘NEVADA’ - Colossal pollinator. Produces a medium sized nut that ripens several weeks after ‘Colossal’. Grafted only.

‘BISALTA #3’ - (Japanese x European) Very large nuts, early and heavy bearer. Good pollinator variety. Grafted, seedlings or layered (own roots).

‘MARRON DU VAR’ - Very large easy peeling variety, originating in France. Late ripening, pollen sterile. Grafted only.

‘SKIOKA’ - Similar in tree form and overall nut quality to ‘Layeroka’, but less productive, good pollinator, nuts ripening a little later with some remaining in the husk. Parent of ‘Layeroka’ and ‘Skookum’. Grafted or seedlings.

‘SKOOKUM’ - Remarkably vigorous timber form. A free husking variety combining the best qualities of ‘Layeroka’ and ‘Skioka’. Ripens between ‘Layeroka’ and ‘Skioka’. Pollen sterile. Grafted or seedlings.

‘MARIGOULE’ - (European x Japanese) Vigorous dual purpose tree - large sweet nuts and good timber form. blight and root rot resistant. Good pollinator. Zone 5-8. Grafted & seedlings.

‘BELLE EPINE’ - Very high quality, reddish brown nuts. Quick to bear, late ripening. Good disease resistance. Pollinator.

‘PRECOCE MIGOULE’ - (European x Japanese) Popular variety widely grown in France and Italy. Precocious of medium to large nuts that ripen early. Highly productive. Fairly high rate of double embryos. Anthracnose resistant. Good pollen producer. Zone 5-8. Grafted. LIMIT 1 of grafted.

Nolin River Nursery
797 Port Wooden Road
Upton, Kentucky 42784
Phone (270) 369-8551 Mon.-Sat. 7-7 C.T. Closed on Sunday
OWNERS:John & Lisa Brittain
john.brittain@gte.net
http://www.nolinnursery.com

We are a small family owned and operated nursery trying our best to meet a growing demand for high-quality grafted nut trees sold at reasonable prices. The name of our nursery reflects the location of our farm in Hart County, KY., about 15 miles north of Mammoth Cave National Park. We were established in 1985, operating primarily as a mail-order nursery. We specialize in the production of grafted nut trees. The advantages of planting grafted or budded trees over seedling trees are several fold. Grafting insures identical replication of superior individual nut trees that have been selected as the best trees compared to hundreds or thousands of seedling trees. The varieties that we produce have almost always been chosen as winners in nut competition at state fairs, state nut grower organizations, ornational nut growing organizations such as the Northern Nut Growers Association. Seedling trees, in contrast, almost always differ from the parent tree from which the nuts were collected and planted, and in comparison with a grafted parent tree, will usually be less desirable in some respects. Furthermore, seedling trees must grow through a juvenile period before they are capable of flowering and nut production. Because the tissue used in grafting or budding a selected variety has already gone through this juvenile period, grafted trees usually begin to produce in less than half the time required for seedling trees. We grow, graft, and grade our own trees to insure the best quality in the trees we sell.

CHESTNUT (Castanea mollissima and hybrid)

‘ARMSTRONG’ KY. 1980. Medium nut; very sweet; possible Chinese-American hybrid.

‘AU LEADER AL’. 1980 Released by Auburn Univ., this very productive Chinese variety has excellent flavor, raw or roasted, stores well and nuts average about 35 nuts per lb.

‘CRANE’ Philena, GA1963. A pure Chinese selection and a consistent heavy producer of large nuts, 30-40lb. For the Ohio Valley and South.

‘EATON RIVER’ CT. 1980. Large nut; early maturing; ornamental; suspected Chinese X Japanese-American cross; very sweet. Consistent producer of high-quality nuts, 30-40 per lb. Our favorite variety.

‘FORD'S SWEET’ IN. 1980. Timber-type Chinese; small, sweet kernel that resembles American Chestnut; heavy bearer, good wildlife food.

‘FORD'S TALL’ IN. 1980. Timber type Chinese, reaching 70' in height, similar to Ford's Sweet, with medium-sized nut.

‘MEILING’ GA. 1949. Large, good-flavored nut; early and heavy bearer; good keeping qualities. Chinese.

‘MENDES’ N.Y. 1996. A very hardy and productive Chinese selection, medium sized nut with a short season.

‘MOSSBARGER’ Glendale, KY. 1983. A very productive Chinese selection with very large sweet nuts. Properly cured nuts peel easily and store well.

‘ORRIN’ Lockhaven, PA. 1963. Large attractive nut, excellent keeping qualities. Precocious and slightly later blooming than other varieties. Short season Chinese.

‘QING’ Ky. 1999 A heavy yielding Chinese variety, producing shiny dark brown nuts that ate X-large (20/lb) and exceptionally sweet. Nut matures early to mid season

‘SLEEPING GIANT’ New Haven, CT. 1960. A Chinese X Japanese X American hybrid. Consistent producer of med-large handsome nuts, about 40 nuts per lb.

Empire Chestnut Company
3276 Empire Rd. SW
Carrollton, OH 44615
Phone: 330-627-3181
http://www.empirechestnut.com/

For those who want to grow their own chestnut trees, we sell selected seed nuts, seedling chestnut trees, and several cultivars of grafted chestnut trees. If you want just a few chestnut trees for your backyard or if you want to plant a commercial orchard we have what you need. We sell chestnut trees for wildlife plantings and for research. A visit to our on-line catalog will provide you with a description of each kind of chestnut tree.

OUR CHESTNUT CULTIVARS

FEATURED CULTIVAR:

'Qing' (pronounced "ching") - The original tree grows in western Kentucky. It appears to be pure Chinese; it's a vigorous grower and a consistent,
productive bearer. It has large nut size (as large as imported European chestnuts), excellent flavor, excellent keeping quality, and it peels easily. Its only reservation is that it has not yet been tested in any trials or orchards.

OTHER OUTSTANDING CULTIVARS:

'Amy' - Pure Chinese, selected from our orchard, medium to large sized nuts, early ripening (a few days earlier than 'Eaton')

'Eaton' - Selected in CT, probably a seedling of 'Sleeping Giant', medium to large sized nuts, early ripening

'Gideon' - Pure Chinese, selected from our orchard, medium to large sized nuts, mid-season ripening

'Peach' - Pure Chinese, selected from our orchard, medium to large sized nuts, mid-season ripening

'Sleeping Giant' - Selected in CT, hybrid with mainly Chinese characteristics, medium to large sized nuts, early ripening

'Paragon' - This is most likely the "Sober Paragon", an American-European hybrid widely planted in the early 1900's. It has a vigorous, upright growth habit, is a consistent bearer of medium-sized nuts, mid-season ripening, very blight susceptible, It has produced many outstanding offspring both in terms of nut production and timber-type growth.

ARCHIVED AND POTENTIAL CULTIVARS - PROPAGATED IN LIMITED QUANTITIES:

'AU-Homestead' - Selected at Auburn, AL; cold-hardy to -20 degrees F, medium-sized nuts, late ripening, reportedly some gall wasp resistance

'Carr' - Old cultivar, medium to large-sized nuts, upright growth habit

'Chandler' - Selected by George Smith in South Carolina

'Crane' - Medium-sized nuts, late ripening, upright growth habit 'Kohr' - Selected by Clarence Kohr in Pennsylvania

'Lindstrom 67' - Not yet named, but potentially outstanding clone from Jerry Payne's planting in Byron, GA, vigorous grower, large nuts

'Lockwood' - A Japanese selection from Connecticut, large nuts

'Nanking' - Was once a very popular cultivar in southeastern USA, medium to large sized nuts, late ripening, tends to over-produce resulting in smaller nut size

'Norris' - Reportedly resistant to chestnut weevils, medium sized nuts

'Orrin' - Similar to 'Nanking', medium to large sized nuts, mid-season ripening, tends to over-produce resulting in smaller nut size

'Smith' - Selected by George Smith in South Carolina

Chapter 2: Horticultural Aspects of Chestnut Production

2.1 Overview

Before purchasing a tree, before planting a tree, before choosing a field to estabish an orchard, sit down, open your business plan and write the purpose of the planting and the goals you wish to meet. Use this as the start of your business plan. Do you know what and where the markets are and how you plan to get your prouduct to market? Will you be too dependent on others to develop a market? Are you expecting to sell wholesale or retail? What is the expected price for chestnut in the next few years? What are you using for sources? Do you have enough experience to start this venture? Are you willing to meet the necessary requirements of the trees? How do you plan to harvest the nuts? Do you feel there is enough help available to provide objective answers to your questions?

If you feel confident enough to pursue your goals then join a grower’s group that will provide you with the needed expertise that you will need in the next few years. Remember, starting a chestnut orchard is still a pioneering venture that may lead to revenue losses and frustration. Currently, there are no large commercial chestnut orchards in production in Michigan and most of the people making money are those who are selling trees not nuts. But if a commercial industry is to start, it seems that now might be the time.

With so many Michigan chestnut orchardists having problems establishing chestnut orchards in the 1980’s and 90’s, Michigan State University researchers decided to focus their efforts on one variety. That variety was ‘Colossal’. If lessons could be learned from ‘Colossal’ plantations, then researchers would be able to teach others about this variety and have a comparison to use for other varieties. Using a newsletter and meeting format, information has been fed to chestnut orchardists through the non profit chestnut research and education organization, the Midwest Nut Producers Council (MNPC). In 1996, members of the MNPC bought a couple thousand ‘Colossal’ chestnut trees or its pollinator ‘Nevada’ from Fowler Nurseries and together learned how to and in many cases how not to treat the trees. We expect the following information to be useful for other varieties of chestnut and wish to hear your feed back.

2.2 Establishing Your Orchard

Site Selection– Many factors determine the suitability of a site for chestnut production. A good, well-drained, relatively fertile soil is most desirable. Generally speaking, the more sandy loam and organic matter there is, the better the soil unless drainage is a problem. Often, soils with considerable clay or organic matter are low and poorly drained. Soil types, drainage, texture, and the amount of organic matter in Michigan soils can vary markedly even within a small area. The importance of a careful soil survey prior to planting cannot be overemphasized as this may help to prevent mistakes that the grower will have to contend with for the life of the orchard.

Chestnut orchards can only be established on well-drained soils where the pH varies from 5.5 to 6.5. From experience, the pH can be lower, but it cannot go much higher without nutrient problems developing. We have seen the burning of young shoots and leaves associated with pH below 4.5. A pH above 7.0 leads to leaf chlorosis and stunted growth. If you cannot meet these basic features with your land, do not attempt to grow chestnut or be prepared to constantly neutralize these constraints.

Transplanting– Nursery trees are available as either container grown, bare root or large tree transplants. Fowler Nursery ships ‘Colossal’, ‘Okei’ and ‘Nevada’ trees as bare-rooted nursery stock after being placed in cold storage for a few months.

Bare Root: Many species of trees including chestnuts respond well to bare root planting. A greater portion and longer roots are retained after digging or removing from the nursery. Also, the roots are easily inspected at planting time. Damaged roots can be trimmed and girdling roots can be removed before planting. Bare-root plants should be planted while they are completely dormant. Large sized bare-root trees might require staking.

Container Grown: The advantage of using plants grown in containers is that 100% of the roots are in the container. Thus, the plant goes through limited transplant shock if given adequate follow-up care. The main disadvantage of container-grown plants is the possibility of deformed roots. “Rootbound” plants have roots circling inside the container. The entangled roots are a physical barrier to future root growth and development. If this condition is not corrected at planting time, the plant may experience slow growth and establishment because of the girdled roots. Some form of root mass disturbance is recommended before planting. A relatively new production system is the use of fabric containers or bags. Plants are grown in the bags, placed in the ground, with a soil backfill. The advantage to this production technique is purported to be a means of harvesting a greater number of roots while using field production practices. The fabric must be removed at transplanting time. This can be somewhat of a problem when the roots have become attached to the walls of the bag, or if roots have escaped through the fabric).
Containerized nursery material may be smaller than bare-rooted stock. The problem with planting small stock is that they succumb to deer, rodents, mowers, hoses, cultivators, etc. easier than larger, bare-rooted nursery stock. It may take them longer to get above deer browse and it will take them longer to get to nut-bearing age.

Large Tree Transplanting: Mechanically dug, these trees require excellent soil conditions and frequent irrigation to help them repair damaged roots. We have moved ‘Colossal’ chestnuts after two full growing seasons and before the third. The roots were hand dug after a backhoe cleared most of the soil from around the root zone. The trees survived their transplanting and produced flowers during their first season in their new location.

The Soil Test—Soil testing is an important diagnostic tool in evaluating nutrient imbalances and in understanding plant growth problems. Soil test results help growers adjust fertilizer application to provide nutrients that are lacking in the trees. Also, soil testing helps growers maintain soil pH within an optimum range (5.5-6.5 for chestnut), which keeps nutrients available for plant uptake. The soil test section is usually placed with the fertilizer section of a report like this, but we place it here to inform you that it should be used before you even plant your orchard.

The soil test report includes soil pH, lime index, available phosphorus, potassium, calcium, and magnesium, liming and /or fertilizer recommendations based on the crop to be grown and soil test results. Michigan State University recommendations are given in “pound of nutrients needed,” not pounds of commercial fertilizer to be applied.

You can take soil samples to either your county Extension office (check the Yellow Pages under "county government listing") or directly to the MSU Soil Plant Nutrient Lab in MSU's Plant and Soil Sciences Building, room A-81(at far north end of the building's basement). The MSU Soil Plant Nutrient Laboratory is self supporting. A fee is charged to each service offered and prepayment is required. Contact your county MSU Extension Service office or the MSU laboratory (517-355 1274, fax 517 355-1732) for a current price list.

Soil testing procedure—Development of a consistent and representative soil sampling procedure is critical to all Center for Soil Testing analyses. The soil samples being sent to the laboratory must be representative of the actual field condition. Soils naturally have high spatial variability for many of the soil aspects being tested. To account for this variability, multiple soil samples from the root zone should be taken randomly throughout a field (a single field is called a “single management unit”). If the field is known to be uniform for soil type, water management and cropping history, then the subsamples can be thoroughly mixed together for a single sample to represent the entire field. If uniform conditions cannot be established for a particular field, then testing of additional samples (still with subsampling) for various subsections of the field should be carried out. Areas of different cropping and management history and soil types should always be sampled separately. Until sampling data are available to prove the uniformity of a management area, sampling should be done with a soil probe, spade or trowel and a clean plastic pail. Sampling depth for field soils is 8 to 10 inches somewhere around the tree. Take a representative sampling (15 to 20 subsamples) of the soil in the area you are testing. Mix subsamples thoroughly in the plastic pail and send one pint of the soil for testing.

The MSU Soil Plant Nutrient Lab does not include direct nitrogen analysis because soil nitrate levels are the best indicator of nitrogen availability. Because they fluctuate widely depending on rainfall and soil temperatures, the best time to take soil nitrate samples is when the crop is growing and within two weeks of initiating your nitrogen applications (March-May). A soil sample taken months ahead of time will not provide an accurate measure of the nitrogen available to the plant. But you should still sample a field to determine its pH and overall soil type and fertility. You should receive your test results in two weeks. The analysis takes 3 to 5 working days from the time the lab receives your samples. The results are then mailed to your county Extension agent for interpretation. Since chestnut is a new crop for this region, interpretations will be difficult to make. Keep your results handy, since the number one problem we saw with chestnut plantings in California was soil conditions.

Planting techniques—The correct planting technique begins with the loading of the plant at the nursery or at the site where you will pick up your trees. Chestnut growers should be very careful with the plant material received. Always protect the roots, and stems during transport. The plant tops should be shielded from winds. When you arrive to pick your Colossals, don’t bring an open back pickup truck unless you have tarps with which to cover the plants. Few plants, whether dormant or vigorous can stand continuous 80-90 mph winds (yes, I’ve seen you drive!) even if the roots were not connected to a water source. Never pick up a plant by the trunk. Trees are particularly vulnerable to damage if growth has started. In the spring the bark is easily injured. If plants must be held or stored on the landscape site, it is best to place them in a location protected from the wind and sun. Do not let the roots freeze or dryout during this time. If the delay in planting is more then a few days, one should heel the plants by covering the roots with bark or some other mulch.

The Planting Hole—Tree holes should be large enough to accommodate the root system with a minimum of root pruning. However, long roots can be cut back enough to balance the root system and to allow planting without crowding or twisting roots to get them into the hole. If an auger is used in wet, clay soil, the inside surface of the hole glazes and seals off, sometimes preventing root penetration. It also leads to the possibility of rain or irrigation water saturating the soil in the hole and not draining out creating a condition of low oxygen. This undesirable glazing of holes can be prevented by digging the holes a few days ahead of planting, when the soil is dry or with low moisture. If this is not practical, part of the glaze can be removed by slicing the edges with a shovel at planting time.

Planting—Planting trees in early spring helps ensure their survival during the first year. Soil temperatures in late March to mid-April are warm enough for root growth to occur, firmly anchoring the tree in its new environment. This early root growth is important to the tree since foliage development and warmer, drier weather demands considerable amounts of water from the newly established root system.

Trees planted in the fall are often subject to low survival if a cold spell occurs early. This is because roots need to become established before the drying, cold conditions common in winter. If fall planting is a must, do so no later than mid-October.

Bare-rooted plant roots should be kept in water or be kept moist prior to planting, and, unless the soil is wet, the tree should be watered at planting. Clean soil, preferably topsoil, should be put around the roots and firmed in with the feet after the hole is about half full of soil. Above all else, do not put chemical fertilizers in the hole at planting time because the roots can be killed by such treatment. Also, the most common problem in establishing new plantings are improper irrigation and lack of weed control. These two problems cause more stunting and plant loss than any others during the first two years of orchard establishment.

The most important consideration in planting trees is the planting depth. Don't plant too deep. It is better to plant in a raised manner so the roots will not drown or suffocate. Dig planting holes 2 to 3 times wider than the rootball and the same depth. Locate the rootball on solid soil and not loose backfill.

A properly planted tree will be more tolerant of adverse conditions and require much less management than one planted in-correctly. Planting technique impacts water quality as it minimizes water, fertilizer and pesticide use.

Spacing—this is an area of orchard establishment that is still wide open for discussion. Trees planted too close eventually develop poor health, have unattractive shapes and, as crowding occurs, nut production and quality will be reduced. If tree crowding occurs with age, whole trees need to be removed as soon as possible. Pruning will not correct for root and limb crowding. Pruned trees will grow rapidly and soon crowd again. Also, remember that pruning your trees will set back nut production at least a year. Other important aspects are soil type, frost pockets, wind and water drainage. In California we witnessed one major chestnut grower thinning his ‘Colossal’ chestnut plantation by removing every other tree. You will have to do the math to determine the amount of production gained versus that lost by purchasing and then cutting out trees. It seems to us to be a reasonable thing to do as long as you remember to keep the pollinators. You can’t cut those out of the orchard.

At one time we thought that 18 foot centers would be enough as our variety trials are planted at 18 foot centers. But chestnuts only produce flowers in the the sun and with chestnuts only 18 feet apart, they soon grow into each other causing reductions in flower and dying branches from shading. With Chinese chestnut varieties which do not always grow as large as Japanense or Japanese-European hybrids (like ‘Colossal’) it would be easier to get away with spacings that are closer together. But 18-20 feet still evaporates within 8 years in most cases.

With more and more ‘Colossal’ orchards being established, it was suggested that trees be planted every 20 feet with the planned ultimate removal of every other tree such that spacing becomes 40 feet apart after they begin to grow together. That requires a serious calculation to determine how much a tree costs and much you gain from twice as many nuts early in the production cycle before every other tree is destroyed.

Another option was to plant 30 feet apart and keep all trees. You will have fewer trees from the outset and fewer nuts during the early years of the orchard, but there would not be the expense of tree removal or losses due to shading and competition.

But in the 2000 growing season a serious problem regarding both spacing and pollination developed. With the 1997-’colossal’ trees beginning their fourth growing season, 3-4 pounds of nuts were expected from each tree in the orchard. Emphasizing this expectation were the large number of flowers which soon turned into burs which stayed attached to the trees well into September. A large harvest was expected, but then in mid-to late September the burs fell empty, unpollinized flat, shriveled nut in most cases. A few growers received 2 pounds of nut per tree but most growers had many empty burs and only a few pounds of nuts for the entire orchard. What went wrong?

We believe that the pollinators were too small and too far from the trees they were expected to pollinate. Analyzing ones grower’s orchard where pollinators and nut producers were in a straight line showed that only the two closest trees on either side of the pollinator ever produced more than 1 pound of nuts and in some cases these “close” trees produced 3 pounds in their fourth year. Close was 24 feet apart. As soon as trees in the straight line were more than 24 feet apart the number of nuts were reduced to less than a pound (usually just a small handful). Because the trees were in a straight line we could not determine the effect of the wind from west to east. There was seemingly no effect of the wind going from south to north as you might expect with the winds blowing from the southwest in the summer. In fact, the worst position for nut production was the north portion of the orchard. The center trees next to pollinators had the best yield.

When looking at the variety trials where most of our yield data were obtained, we see that the trees are randomly planted, pretty close to each other due to the lack of space available at the research stations. So each tree can pollinate any other tree and they are close to each other. Here we thought that pollen blows 500 feet on the wind, and maybe it does, but not from small, young trees.

This requires a re-visit of the spacing situation taking into account both tree growth, tree removal and pollination. Earlier we published a planting plan that would accomodate both problems. In this planting plan we suggested two planned removals of trees. At first the trees would be planted close together and then a few years later, some trees would be removed and a few years later more trees would be removed and the remaining trees would have great access to sun, soil and nutrients.

The spacing examples in the figures below may help you understand some of your planting options. 1 = first tree for planned removal in year X. 2 = second tree for planned removal in year x + y. 3 = a permanent tree. Remember that both pollinators and production trees must be left in the orchard. In the first several years, pollinators should be no further than 25 feet from production trees.

Initial planting

After X years

After X + Y years

By following this scheme, you keep your pollinators and nut bearing trees as close together as possible during the years of nut production as you remove trees due to overcrowding.

Wind breaks—Populars have enjoyed an every increasing popularity as a wind break around orchards. However, we found two locations where poplar tree roots, from trees over 30 feet away, reduced growth and flowering potential of ‘Colossal’ chestnut trees. We do not suggest planting poplars as a wind break. If you need a wind break try white pines.

2.3 Pruning Your Chestnut Trees

If you purchase chestnut trees from Fowler Nursery, these bare-root trees will come cut-off at the top with a rather ratty looking torn cut. This needs to be re-cut at planting time down to fresh clean tissue. If not, secondary, weak pathogens will infect the bark and cause bark cankers (infections). Once this cut is made, you may wish to remove weak branches below this fresh cut. But after these cuts are made, what should you do?

Assume your newly planted tree, whether it is a Colossal or other type of chestnut variety, looks something like the one in the next column over. The diagram assumes there is new growth coming from the top of the main stem and various branches and stems below the top of the main stem. Should you prune it? In the first year? Should you let it grow anyway it wants to grow, since as long as there are leaves, it’s good?

Lorin Amsberry, chestnut horticulturalist from Fowler Nursery has suggested to us in the past that we want to allow water to flow from the roots to the strongest stem near the top of the main stem; keep that shoot growing! Think of your root system as a water pump. Any stems greater than 1/2 the size of the main stem should be considered “leaks” in the main water pipe. All of those stems are stealing water from the shoot you are trying to push. The shoot which you are pushing will become an extension of the main stem. Small branches can stay as they do not significantly reduce the amount of water to the top of the tree. That root system should be used like a water pump. When you buy a tree from a nursery, you should use the resources of the nursery where the plant had been growing. A nursery like Fowler Nursery puts a lot of nutrients into the soil so that the system you purchase does not require anymore more nutrients the rest of the year. When you buy that tree, you are buying those nutrients and paying for that water pump.

Another theory on early pruning suggests that the tree should just be allowed to to branch and that training should occur a couple years later. This is the method most often used by default. If you don’t prune or are afraid of pruning too much you generally end up following this technique. That is not to say that some growers don’t prefer the “lollipop” effect. Some suggest that this offers more leaves and therefore more food for the roots. But, as Lorin Amsberry points out, the roots don’t need much attention when the transplants are planted, other than a good source of water. Getting some height on those trees would be his recommendation.

There is no scientific evidence, yet, from the Midwest suggesting that either method is better for the tree in the short or long term. I have seen both methods used on ‘Colossal’ in the same orchard in Michigan and both methods produce trees with burs in three years, however, the trees pruned less (more lollipop-like) have more burs since there are more branches. Sooner or later those lower branches will need to be eliminated due to shading or head bumping for tractor riders.

In real pratice then, how should you let your young trees branch? That depends on the goals set for your orchard and trees. Do you want your orchard to be free of branches for at least 5 feet or more? Some growers consider that important so they won’t bump their head when mowing or for future harvesting techniques which might entail the use of a tree shaker. Let’s look at some real examples:

Photo 1

These three branches (arrows) could have been eliminated at planting as they may have reduced the growth of the main shoot (to the right of the pole). The branch directly competing with the main stem (upper arrow) must be removed because the angle of the branch may cause a split in snow, ice or wind storms. The other two branches can be removed over the next two or three years

In the the photo in the next column (photo 2), you can see the strong shoot off the main stem that can result from eliminating all branches below this shoot, in the first year. In this case the main shoot has continued (acutally the dead end of the main stem should have been cut closer, arrow) to grow and has set branches at about 5 feet above the ground.

Photo 2

In photo three, below, you can see what may result if two branches are left at the top of the main stem. One is slightly larger than the other and it is going off to the side. The smaller of the

Photo 3

two branches is the straightest, but also the weaker of the two. In photo 3, one of these two branches needs to be eliminated and it will be a tough decision. Probably the stronger one, going off to the left, will be retained and tied to the pole in order to straigten it out in time.

In general, my suggestion would be to reduce those water robbing side branches; if not in the first year, then by the second or third. Get some height on the tree and support it by staking it with a ten or twelve foot metal conduit post and let the tree begin its branching at 5 or 6 feet. If you have a better plan that works, use it and share it with us!

2.4 Irrigating the Trees

Horticulture researchers have estimated that 75% of the roots may be lost when digging field-grown nursery stock. Cultural practices by the nursery-person, such as root pruning, irrigation, fertilization, root-ball configuration, and digging techniques, influence the percentage of harvested roots. Water stress, due to removal of most of the water absorbing roots, is the primary cause of transplant failure. Most water absorption capability within a transplanted root-ball results from very small diameter roots. These fragile roots are the first to suffer from excessive water loss in newly transplanted trees.

Trickle irrigation—The frequent application of small quantities of water on or below the soil surface is called trickle irrigation. This type of irrigation system delivers water, and can distribute nutrients and other chemicals directly to the root zone of the plant. Applied quantities closely match evapotranspiration and nutrient demand. Water is distributed through emitters placed along the water delivery (lateral) pipe in the form of drops, tiny streams or miniature sprays. Trickle methods include drip, bubbler and spray irrigation. In some cases the drip line may be buried under the soil surface and called subsurface trickle irrigation Trickle irrigation systems operate at low pressure; therefore, they require less energy for water pumpage when compared to other high pressure irrigation systems. Also, because of their precise application, they conserve water and nutrients when managed well. Because of the potential water and energy savings, trickle systems have become popular, and the number of acres under trickle irrigation is increasing every year.

Drip irrigation.- provides excellent water management and conservation with a minimum of water. More and more growers are using drip irrigation on row crops. Drip irrigation applying small amounts of water slowly and frequently through emitters spaced along polyethylene tape or tubing is now the main method used to irrigate. The reasons for the growing popularity of drip irrigation are several. Drip irrigation offers improved yields, requires less water, decreases the cost of tillage, and reduces the amount of fertilizer and other chemicals to be applied to the crop. Because drip irrigation makes it possible to place water precisely where it is needed and to apply it with a high degree of uniformity, it lessens both surface runoff excess water running off the lower end of the field and deep percolation water flowing down through the soil past the root zone where cannot be used by the crop. Drip irrigation can also be used in conditions unsuitable for other irrigation methods on steep and undulating slopes, in very sandy soils, and in fields with widely varying soils.

These features make drip irrigation potentially much more efficient than other irrigation methods, which can translate to a significant water savings. But drip irrigation can only achieve this level of high efficiency if the system is carefully designed and managed so as to prevent such problems as emitter clogging and differences in emitter flow rates stemming from pressure variations in the irrigation system or from differences in emitters and flow passages originating in the manufacturing process.

The Positive Aspects of a Drip System
· Very high potential for water savings
· Easier for above-surface installation, retrofitting capabilities and repairs
· Uniformity improves 20-50 percent
· Overspray reduced almost 100 percent (reduces liability)
· Better infiltration rate with lower precipitation rates
· Reduced weed growth with pinpoint irrigation
· Curtails puddling
· Diminishes evaporation
· Requires less pressure from point of connection
· Fewer drainage problems
· Drier environment, less disease
· No blocked spray patterns
· Less runoff - almost eliminated
· No water loss from wind drift
· Politically correct to be water conscious and upgrade or retrofit where possible
· Ability to deliver water into mixed hydrozone planters (control by emitter size)

Micro-irrigation - applying small amounts of water slowly and frequently through emitters spaced along polyethylene tapes or tubing makes it possible to apply water precisely where it is needed and to apply it with a high degree of uniformity, lessening both surface runoff excess water running off the lower end of the field and deep percolation - water flowing down through the soil past the root zone where it can no longer be used by the plant. Converting from conventional surface irrigation to a micro-irrigation system therefore can greatly improve how evenly water is applied over a field and how efficiently water is used. But this potential can only be realized if the micro-irrigation system is carefully designed, maintained, and managed.

Before any irrigation system is designed, the planting plan must be reviewed. The optimum time to create the appropriate irrigation system is while designing a new landscape. A design should take into consideration the problems the installation and maintenance contractors may or may not encounter. If irregular-shaped planters are designed, then the appropriate plant materials and irrigation system should be selected. Plant materials at maturity must be considered for their size and compatibility with other plant species and, of course, which irrigation system will work best when everything has grown tall and thick and is blocking the irrigation coverage.

Improper watering practices can cause more harm than not watering at all. Overwatering, a main cause of transplant failure, forces oxygen out of the soil and results in oxygen starvation of roots. This causes death of roots and leads to an eventual decline of the tree. The yellowing of foliage, developing first low and on the inside of the tree and progressing to the outer leaves, is an indication of oxygen starvation. Avoid frequent light waterings; this promotes shallow root systems susceptible to dessication in winter and heat stress in summer. Irrigation during the first year should be applied often at least every 1-2 weeks), but each irrigation should be at short duration. Thus, frequent irrigation will replenish the dry areas around the roots without waterlogging the soil. It is best to determine the timing of watering by the moisture level of the soil just above the root zone--the area containing most of the tree’s absorbing roots, generally 6 to 10 inches below the soil surface. Dig down 6 to 8 inches at the edge of the planting hole. If the soil at that depth feels powdery or crumbles when squeezed in your hand, the tree should be watered; soil that forms a ball and clings together when squeezed contains adequate moisture. A vigorous root system, important in establishing new transplants, can be favored by deep watering--watering to a depth of 12 to 18 inches below the soil surface. A commonly used method of deep watering is flooding the soil surface until water eventually soaks down to the desired depth. However, flooding is wasteful of water and temporarily drives oxygen out of the soil, smothering tree roots. Placing water at the proper depth initially is a more efficient way to deep water.

2.5 Preventing Sunscald

Phone calls come in periodically indicating that chestnut blight has emerged in an orchard. I will go to the orchard and usually find a canker similar to chestnut blight on the base of the tree that has no apparent chestnut blight. It is a problem called sunscald or “southwest disease”.

As was mentioned above, young transplants and thin-barked trees, are susceptible to an injury called "sunscald" during the winter and early spring. Chestnuts have big problems with sunscald in the midwest. In California, the scald occurs in the summer but in Michigan we believe the scald occurs in the winter and early spring. The surface temperature of trees is elevated above that of the surrounding air by the absorption of sunlight. This rise in surface temperature occurs long enough to make cells in the bark active and thus vulnerable to injury during the sudden nighttime temperature drop. Growers need to paint their trees with a white latex paint diluted 50% with water. Paint high enough to protect all parts of the trunk (up to and beyond the crotch). The paint should be an indoor, cheap white latex diluted with water. This reduces the amound of preservatives in the paint that may damage the tree.

Photo 4

Don’t Forget About Your Tree Guards
Don’t forget to take off and adjust the white tree guards. These tree guards work well to prevent physical damage of the main stems caused by either mammals or equipment. But they should be adjusted at least twice each growing season. They do not expand on their own. Here you can see the spiral effect on the trunk of a tree this summer.
You can even see the protrusion of the bark through the tree guard holes.

2.7 Controlling Weeds

Weed growth around a young tree steals soil moisture, nutrients, and sunlight, all which the tree needs for rapid growth. In the first year of planting, weeds can be kept out by pre-planting chemical control, or by hand weeding, tillage, surface mulching, etc. In the second year, and succeeding years, chemical herbicides can be applied to prevent weed growth. It is usually hazardous to use chemical weed control the first season because of possible injury to unestablished trees. Therefore, your weed control should start the year before your trees are placed in the ground.

Maintainning young trees free of competition from weeds or sod is very important for the vigor of the tree. Weed-free trees will result in larger trees and a good oportunity to produce nuts on young trees. It has been shown repeatedly that maintaining weed-free conditions in an orchard will promote the production of increased nut yields as a result of increased of tree size.

How do weeds reduce the growth of trees? Weeds compete directly with trees for soil moisture and nutrients and often serve as hosts for insects, diseases and varmints. It is imperitive to provide optimum growing conditions the first few seasons if you are going to produce healthy trees with strong trunks and scaffold branches.

How much of my field needs to have weed control? Controlling weeds in an area 3 to 4 feet from the trunk is adequate for the first 3 years. As the tree becomes larger and its root system spreads over larger areas, weed control must be increased to an area larger than 4 ft from the trunk or at least to the drip-line of the tree. This should also help in surveyng your trees health and picking up nuts.

Weed barriers—The best way to control weeds is by reducing sunlight to the weeds growing around the trees. Weed barriers or mats can be bought at orchard supply houses or through orchard management catalogs. This is generally more expensive than chemical weed control (see below) but the benefits to you and the environment may out weigh the cost of the barrier. By using weed barriers, you may find yourself elgible for organic certification in three or four years down the road. Weed barriers should last more than one season and how you treat them will determine their overall longivity.

Mulching is always a good idea, but in our observations with mulching, we find few growers willing to stay up with the mulching in terms of weed control. A nice mulch offers a great environment for weed growth. If the weeds in the mulch are not removed periodically, they will set deep roots in the moist soil beneath the mulch and they may be harder to remove than if the mulch was not in place.

Chemical control—Herbicides can hurt young trees and you must be deligent in not getting the material on the young trunks or leaves. Generally, trees gain herbicide tolerance with age. Newly planted trees are more suceptible to herbicide injury, but generally gain some tolerance when two- to
three-years old, and become much more tolerant when older. Trees growing in sandy soils, which are low in organic matter, are more suceptible to soil-applied herbicides than trees growing on heavier, loamy soils.

There are a limited number of herbicides registered for use on chestnut trees. Due to this limitation, we can only work with the following herbicides:

Pre-emergent
Surflan (Oryzalin)
Simazine (Princep)

Post-emergent
Roundup Ultra (glyphosate)
Gramoxone extra (paraquat)

Pre-emergents are a class of herbicides that kill the germinating weed seeds that fall to soil and sprout. They will not kill established weeds.

Surflan (40.4 % a. i.) can be used safely on newly planted fruit trees after the soil has settled and no soil cracks are present which would provide an avenue to the root zone. It is effective in controlling annual grasses and many annual broad-leafed weeds. Its strength is in combination with gramoxone (formerly known as paraquat) or Roundup where the paraquate or Roundup will kill established weeds and then the Surflan will prevent weed regrowth. Rain or sprinkler irrigation are need to move Surflan into the weed seed germination zone. The water also activates the herbicide.

Simazine (90 % a. i.) is effective primarily on germinating, annual broad-leaf weeds and grasses. It can be combined with paraquat or Roundup to control already established weeds. This herbicide does not build up in the soil from annual application. Plant injury has been when applied on extremely sandy soils, therefore manipulating the rates of application on different types of soil is very important.

Emergent herbicides control plants that are already growing. Some will kill all plants and others are specific for type of plants.

Roundup (41 % a. i.) controls both annual and perennial weeds, grasses and broad leafed plants. It has a systemic quality in that it moves from the leaves to the roots. This is called translocation. This herbicide can cause serious damage to nut and fruit trees if contact occurs on any green tissue (leaves or shoots), or on young trunk bark. Apply only near trees that have been planted for 2 or more years. Be careful of material drifting to young green tissues of the trees. It can be used all year long, but you should attempt to use this to knock down the early weed load, before the trees break bud. This material works takes about 9 -12 hours to work on sunny days, but the weeds may take two weeks to die. You should notice a slight yellowing within a few days. If you mow the weeds before application, wait for the weeds to begin active growth for best uptake of the material. It does nothing by itself to prevent weed seeds from germinating.

Gramoxone extra (formerly known as paraquat [37 % a. i.]) provides rapid kill of annual and perennial weeds, and may be utilized in all fruit plantings. This material should be applied when weeds and grasses are suculents. It has no activity on the roots to prevent further weed growth and eventually many of the weed roots will send up shoots which will be evident in 30 to 40 days after application. Do not allow paraquat to contact foliage or areas of the trunk where bark has not formed. Painting trunks of young trees with latex paint or using tree guards lowers the possibility of injury.

Below, we have provided you with some information to help you choose and mix your herbicides.

Pesticide Table

Volume Table

Springtime treatment for orchards with established young trees with an existing weed problem—By following these simple steps, you can gain control over the weeds in your orchards. First, mow your weeds getting very close to the trunks of your trees. You may want to hand cut around the base of your trees. This is a good time to adjust your tree guards or paint the trunks (since you are bending over near the trunks). About a week later, after weed growth has re-initiated, put your herbicides on the weeds. In this case I would use Roundup-Surflan, Roundup-Simazine, Paraquat-Surflan or Paraquat-Simazine. Why Paraquat? Just to play it safe. We know that this herbicide burns green tissue, but it does not kill the entire plant. You have to be very careful to handle paraquat when you spray it, because if you burn your trees, this stress can eventually kill them. The combination of the above listed herbicides (Roundup or Gramoxone) with either Surflan and Simazine is designed to stop current weed growth and the continuous germination of weed seeds for the rest of the summer. Roundup and Gramoxone will kill current green tissue and Surflan and Simazine will kill germinating weeds seeds later, especially if used at least twice a year (early spring and middle of summer). In combination, these pre-emergent herbicides will reduce your overall weed problem.

Remember, weed barriers are also effective tools in reducing weeds, but your labor will be greater. We strongly suggest attempting control with some trees using weed barriers to see if that form of control will work for you.

2.8 Fertilizer

Fertilizer is generally thought of as plant food. Actually, most of the plant’s food is made by the process known as photosynthesis. Through photosynthesis, the plant removes carbon dioxide from the atmosphere, combines it with water and captures the carbon, hydrogen and oxygen atoms used to build the plant. It is through this process that the plant manufactures glucose, which is then used as an energy supply as well as providing the essential building blocks of the plant skeleton. Other atoms and molecules are also needed and some may be in short supply because photosynthesis occurs everyday (unless dormant) and the other molecules must be scavenged through the root system. These other nutrients such as nitrogen, phosphorus, sulfur, potassium and a host of others must be found in the soil and then removed from the soil by the plant’s root system in combination with a fungal symbiont known as mycorrhizae. It is ironic that one of the most limited of these nutrients is nitrogen; the most abundant atom in the atmosphere. Supplying nitrogen to plant systems usually induces a flush of growth whether it is redwoods or algae. This is one of the reasons why algae begin to grow in lakes when excessive nitrogen is released to the water through fertilizer use at home as well as agricultural runoff. For this reason, nitrogen is the focus of our story on fertilization. Too much, and it not only hurts the growth of the plant, it can cause large scale environmental problems in watersheds. Too little, and your plants may be harmed directly through a lack of growth or indirectly through stresses that may be applied now or years later. Most of this information is taken from many sources, few of which deal with chestnut trees. We provide it for your interests and consideration.

Nitrogen-based fertilizers—Nitrogen is one of the macronutrients required for proper plant nutrition and growth. Nitrogen becomes part of many organic compounds within the plant cell. Somewhere between 1 and 5% of the total dry weight of a leaf can be accounted for by nitrogen. The plant takes up nitrogen from the soil in two forms, nitrate (NO3-) and ammonium (NH4+). Nitrogen plays an important role in many of the basic molecules of the plant cell such as amino acids used in making proteins, nucleotides used in making DNA. Nitrogen is also an important component in molecules that make up various pigments and in generating cellular energy. Nitrogen is present in so many compounds that one begins to understand why it is that a lack of nitrogen will lead to growth deficiency symptoms. to make up for a lack of nitrogen the plant has devised various methods for the efficient use of nitrogen. For example, older leaves will exhibit a general chlorosis and may turn yellow and fall off since plants will commonly transfer nitrogen from older leaves to younger leaves to meet the nitrogen requirments of the new growth.

Requirement and Function—Nitrogen, also known as an essential major element, can be found in both inorganic and organic forms in the plant. It usually is found in molecular combination with carbon(C), hydrogen (H), oxygen (O), which are brought into the cell through photosynthesis. Sometimes nitrogen is found in combination with sulfur (S) in specific amino acids used to build enzymes and pigments such as chlorophyll. Although inorganic nitrogen can accumulate in the nitrate form (NO3-), organic nitrogen, that is, nitrogen in combination with hydrogens (NH4+), predominates in the cell due to the high concentration of the super larg molecules known as proteins.

Plant Content—Nitrogen consists of 1.50% to 6.00% of the dry weight of many crops. Usually the amount required in most plants for optimal metabolism, also called the sufficiency value, is from 2.5 to 3.5 percent when measured in leaf the tissue. A lower range of 1.8 to 2.2 percent is commonly found in most fruit crops. The highest concentration of nitrogen is found in the new leaves, and the nitrogen values generally decrease with the increasing age of the tissue or tree.

Interactions: Many of the cellular molecules that we have already mentioned also require phosphorus (P). Generally, these important molecules are made up of carbon, hydrogen and oxygen brought into the plant cells by photosynthesis. The nitrogen and phosphorus need to be taken up from the soil by most plants. Generally, more nitrogen is needed in the cell than phosphorus because nitrogen is used in more molecules than phosphorus. Plants have an enormous nitrogen craving because nitrogen is in such demand. However, the molecules that use phosphorus are some of the most important molecules in the cell. When nitrogen is added, plant growth is stimulated, and the more a plant grows due to this nitrogen addition, the more phosphorus will be needed. Therefore, when nitrogen is added you may notice that phosphorus is somtimes also added for good growth. Whether or not phosphorus is added is dependent on the amount of phosphorus available in the soil. Michigan soils, as a rule of thumb, are not phosphate poor. Potassium (K) is generally added because the more a plant grows, the faster the metabolism and potassium is involved in many of the cell’s active functions such as moving compounds into and out of cells. Therefore, once nitrogen is added ,it is important to provide the other macronutrients needed if the plant is to fully utilize the nitrogen.

Available Soil Forms—Nitrogen exists in the soil as either nitrate (NO3-) or ammonium (NH4+). However, soil characteristics such as soil pH, type of soil, temperature, and the presence of other chemicals in the soil can influence the uptake of either form of nitrogen.

N-Deficiency Symptoms—Plants deficient in nitrogen are slow growing, weak, and stunted. Typically, the plant foliage is light green to yellow in color. The initial and more severe symptoms of yellow-leaf deficiency are seen in the older leaves, since nitrogen is diverted from the older tissue for transport to the actively growing portions of the plant. Nitrogen deficient plants will mature early with yield and quality of fruit significantly reduced.

Symptoms of Excess—Plants with an excess of nitrogen are dark green in color with succulent foliage, which is more susceptible to disease and insect invasion than plants with optimal amounts of nitrogen. The plants may easily bend or break (lodge), and are susceptible to drought. If ammonium (NH4+) is the only or major form of nitrogen available for plants to take up from the soil, a toxic condition may develop which results in a breakdown of vascular tissue, thereby restricting water uptake. The over utilization of carbohydrates is possible when ammonium is the primary form of nitrogen leading to plant growth reduction.

General nitrogen effects—An understanding of the general relationships between nitrogen and tree response is fundamental in managing nitrogen. Tree growth, flowering, fruit set, fruit growth, and fruit quality are all influenced by the nitrogen status of the trees. Numerous factors must be considered in developing appropriate nitrogen management programs. Methods and rates of nitrogen application, nitrogen sources, and economic factors must be included in the decision process.

Vegetative growth: Tree vigor is generally measured by amount of shoot growth or gain in trunk circumference per unit of time, usually one year or growing season. This relationship is important in developing the potential fruit-bearing canopy of newly planted and young nonbearing trees. Cropping potential of young trees is directly related to canopy development, especially in chestnut, which in turn is directly related to the nitrogen status of the trees.

• Low nitrogen supply: Inadequate nitrogen supply when the tree is young may hinder the future cropping potential of the tree because a poor canopy will develop. Limited nitrogen availability may also encourage premature defoliation in the fall, and increases the susceptibility of the trees to injury when exposed to low temperature stress.

• Excessive nitrogen supply: Increases vegetative growth, extends late season growth, delays leaf fall and the maturation of woody tissues, which in turn increases the susceptibility of trees to cold injury during the late fall and early winter period.

Flowering and fruit set: Fruit set has been shown to increase with increasing nitrogen status of the flower buds. The period of receptivity of the ovules for fertilization is relatively short when flower buds are weak. Improving the strength of flower buds by increasing their nitrogen content increases the length of time that the ovules remain receptive for fertilization.

If levels of nitrogen are low; summer or postharvest applications of nitrogen may be beneficial.

• Inadequate nitrogen: Limits flower development and increases the tendency toward biennial cropping.

• Excessive nitrogen: can delay flowering of young trees. In trees of bearing age, excessive nitrogen may also stimulate development of excessive shoot growth leading to reduced flowering and fruit set.

Evaluating nitrogen status: It is important that the nitrogen in the plant be monitored in order to determine if the nitrogen levels are limited, optimum or excessive. To do this, a standard protocol needs to be developed and is generally worth the time and trouble. Below, we have outlined some methods you can use to determine the nitrogen levels in your trees.

Leaf analysis: Nitrogen content of leaves from the current season’s new growth is generally used as the basis for evaluating the nitrogen status of fruit trees. It is important to recognize that the procedure used in collecting these samples needs to be used in all collections if the information is to be compared and used in establishing standards. Most standards are based on mid-shoot leaves collected from 60 to 70 days after petal fall. Obviously, as chestnut growers we would be collecting leaves in September if we used that standard. So we must make up our own. Probably sometime in late July would be best. Older leaves collected at the same time, or mid-shoot leaves collected at a later time will have lower nitrogen contents. Likewise, younger leaves collected at this time, or mid-shoot leaves collected earlier than this will have higher nitrogen contents. If it is necessary to collect samples later than the specified time, the last fully developed mature leaf toward the shoot tip should be sampled.
Standards used in interpreting results of nitrogen analysis must account for differences among fruit tree types, stages of tree development, and the purpose for which the fruit is intended. Nitrogen levels of 2.4 to 2.6 percent, or higher, may be necessary to support adequate growth of the young nonbearing tree. As trees begin to produce fruit, levels of 2.2 to 2.4 percent may be appropriate to support continued growth while supporting fruit set.

Several factors may influence the level of nitrogen in leaf samples
• Shortage of soil moisture, whether as a result of inadequate rainfall or irrigation, or from competition by sod covers or weeds, reduces availability of soil nitrogen to the trees.

• Injuries to the roots or trunks restrict nitrogen uptake and result in lower leaf nitrogen contents.

• Leaf nitrogen contents are also influenced by the level of cropping, being lower in trees that are carrying a light crop and higher in trees that are carrying heavy crops.

• The lower concentration of leaf nitrogen in lightly cropping trees is the result of dilution of the nitrogen in a greater amount of vegetative growth than that produced by trees carrying full crops.

Tree age and vigor
• With newly planted trees and young nonbearing trees, the primary objective is to encourage rapid development of the potential fruiting canopy and early fruit production.

• When the trees have reached maximum allowable size, greatest emphasis must be placed on fruit quality while still maintaining adequate tree vigor to support production of consistently high yields of top quality fruit.

• During the first stage of tree development, nitrogen fertilization rates are primarily based on maximizing growth, to the limits imposed by climatic conditions in the area. During the second stage of tree development, somewhat lower rates of nitrogen application become necessary in order to limit fruit size while still encouraging canopy development.

• Finally, with mature trees, careful control of nitrogen fertilization is necessary to avoid undesirable effects on the fruit quality.

Soil management practices
• Practice that reduces competition by sod covers
or weeds generally results in increased growth and productivity.

• With young trees, practices such as cultivation or maintenance of weed-free bands around trees or in the tree rows may increase rates of tree growth by 40 percent or more, by reducing competition for water and availability of nitrogen.

• In mature orchards, effective weed control has allowed reductions of 60 percent or more in amounts of nitrogen fertilizer application.

• However, the adverse effects of sod or weed competition have not been overcome solely by increasing rates of nitrogen application.

• Mulches of either organic or inorganic materials provide similar increases in availability of moisture and nitrogen.

• Mulching or sod increases soil organic matter levels compared to clean cultivation, and orchard soil management greatly influences nitrogen fertilizer requirements.

Note: Ground cover species differ in depth of rooting and in water requirements. Legumes have higher water requirements than grasses and use more of the available soil moisture, consequently reducing availability of soil nitrogen to trees.

Planting systems
• Although planting systems may not directly influence nitrogen requirements, various systems and planting densities may have appreciable effects on nitrogen requirements. If you are broadcasting the fertilizer, that is spreading it out across the orchard floor, less of it will get to the roots of the tree if the trees are widely spaced.

• Differences in cultural practices and the type or severity of pruning to maintain the trees also influence the need for nitrogen.

• In general, the total nitrogen requirements of orchards decrease with increasing planting density, and timing of N availability becomes more critical.

Rates of nitrogen application
Nitrogen application rates must be adjusted to account for the differences in tree size and soil management practices.

Nitrogen application method: There are several standard ways available to apply nitrogen and other nutrients to your trees in your orchard and probably dozens of less than standard ways that might work for you. Below, we have attempted to describe some of these methods. If you have applied nitrogen to a crop before, some of the information may be too basic, however, if you haven’t or if you only applied it in a haphazard manner, following the guidelines below may help you obtain the maximum growth of your trees from your investment in nitrogen. These guidelines are based on soil application of the nitrogen. While some people may apply it to the leaves, we have no experience with this type of application on chestnut and would rather leave it for future experiments.

Timing
• Timing of nitrogen fertilizer applications to the soil surface influences the type of response that trees are likely to exhibit.

• In most tree crops, early season growth potential and strength of flower buds are largely determined by the nitrogen reserves that the buds contain when growth begins that season. This is a standard statement used for most fruit trees. However, most fruit trees flower in the spring. Chestnut flowers in the very late spring or early summer. We are not sure, but we may be able to have some influence with our spring nitrogen application on the strength of the flower bud. This still needs research, but we may be able to influence the current season flowering with spring application of nitrogen.

• In most tree crops, nitrogen fertilizers applied during the dormant season (February or March) will stimulate vegetative growth and generally do not influence the nitrogen status or strength of current season flower buds or fruit set. This may be true for chestnut, too, we don’t know.

• Applications during the summer, particularly after current season shoot growth has been completed, are more likely to result in improved nitrogen status of the buds for the next season.

• However, applications of nitrogen late in the summer may delay or reduce fruit development, increase the preharvest fruit drop, delay maturation of buds and woody tissues and/or stimulate late season growth, thus increasing susceptibility of woody tissues and buds to cold injury. In regions where cold injury is of concern, summer applications of nitrogen must be carefully managed.

• Late fall applications of nitrogen may delay hardening of buds and woody tissues and increase the potential for desiccation during the winter, particularly if made before trees have become completely dormant. Late fall Therefore, the risks involved with late season applications of nitrogen are greater than those associated with applications during the early spring prior to the beginning of current season growth. So until research suggests some reason for late season application of nitrogen, remember to add nitrogen early in the growing season.

Placement of nitrogen fertilizers
• For most efficient use, nitrogen fertilizers should be spread over the area where the herbicide treatment eliminated the weeds (weed-free zone) or along the cultivated tree-row strips where the majority of the active tree roots are located. Application to weeds or grasses will act to fertilize the weeds and the tree roots will get the leftovers. For this reason broadcasting over the entire orchard floor is less efficient, requires considerably greater rates of application, and is more likely to benefit ground covers than the trees.

• Applying nitrogen to organic mulches, such as shredded bark or leaves, will act to generate microbial degradation of the mulch. The nitrogen will be used primarily by the fungi and bacteria active in the mulch. If you are using organic mulches, apply the nitrogen to the soil and then put down the mulch.

• Fertilizer should be placed near the tree’s feeding roots. The feeding roots can extend beyond the spread of the outermost branches by as much as 40 to 50%. Shallow-rooted species such as elm or maple typically have roots that extend well beyond the spread of the branches. In such cases, extend the area fertilized to match the estimated root spread.

What fertilizer to choose: Our members represent growers who have a great deal of experience in farming as well as some who are just learning about farming. Those who know about farming know to buy their fertilizer from grower supply companies usually housed at grain elevators. Other members, whose only experience with growing is through ornamental and vegetable gardening, may have only bought fertilizer from gardening supply stores or hardware stores. These can be two very different types of experiences. At an elevator you will get a better price for the nitrogen, but you generally have to buy or order more of the material. You will only find it in 50lb bags or they will make it to order if you order a ton of the material. At the garden shops you can find it in 10 lb. bags or boxes but you will pay more for it (up to 10 times more). If you have 10 trees that are 4 to 5-years-old, this year, you will probably need to apply at least a pound of fertilizer (depending on what formulation of nitrogen you use) to each tree. Therefore, you will need at least 10 pounds of fertilizer. Obviously, if you have 50 trees you will need more than 50 pounds. If you consider yourself a commercial grower, you must consider the cost of the fertilizer in relation to the selling price of the product produced by the tree. If you purchase the fertilizer at a garden supply store and pay twice to 10 times the amount you have to, you will be feeding your trees more than they will ever feed you.

If you go to a garden shop you may find fertilizer in a bag labeled for fruit trees, etc. This is one of the reasons why it is more expensive. If you go to an elevator you will need to know what to pick up or what to order. Below, we have given you some information that you should be able to use at an elevator.

Fertilizers: Fertilizers come in two types, the unmixed and mixed fertilizers. The unmixed fertilizer will have only a source of nitrogen and maybe sulfur, but there will be no phosphorus or potassium added. A mixed fertilizer will have nitrogen mixed with phosphate and potassium. Which is right for you? At an elevator you can find bags of mixed and unmixed fertilizers or order your own mixed fertilizer. What are the advantages and disadvantages of each?

Unmixed fertilizers: There ar