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Field Performance of may be a crop worth investigating for Grafted and NY growers looking to diversify. Several Chestnuts in New York considerations must be examined before Ian Merwin, Miranda Kahn, and Rachel Byard embarking in this new Department of , Cornell University, Ithaca, NY 14853 direction. This report discusses various cultural practices of interest. merican (Castanea dentata) chestnuts for the sake of their pungent was once a dominant in forests , interesting foliage, and wildlife Aof the Eastern US, where its small observation or hunting opportunities but flavorful nuts were an important food during autumn. estimating heritability in these chestnuts. staple for wildlife, Native Americans and Because chestnuts are strictly a minor We planted 25 grafted and 25 seedling subsistence farmers. A devastating blight crop in the US, little horticultural of each variety in five randomized caused by the fungus Cryphonectria information is available to assist growers replicate plots each containing five trees, parasitica was introduced accidentally in successful production. Those for a total of 300 trees. Within each plot from Asia into North America around currently growing or interested in of five trees, two were pruned and trained 1900 on trees imported by breeders planting chestnuts often have trouble to an open-center form and two as central seeking to improve nut quality of the finding answers to basic horticultural leader trees, while one tree was left through questions because little research has been unpruned and untrained. hybridization with its Asian cousins. done on this crop in North America. This Is it better to plant grafted or seed- decimated our native report describes our attempts to answer ling chestnuts? With most crops, trees in just 50 years because they had some of these basic preliminary questions commercial growers plant trees that are never been exposed to the pathogen and about the feasibility of chestnut propagated by grafting mature budwood had no genetic resistance to it. production in the Northeast. onto , because grafted trees will Fortunately, the Asian chestnut species be “true-to-type” and begin to bear fruit (Castanea mollissima and C. crenata) are Experimental Procedures sooner than . Grafted trees are resistant to this disease. With European “clones” or genetically uniform popula- chestnut (C. sativa) stands now slowly What varieties are best for our tions, their performance is usually more succumbing to chestnut blight, the Asian growing conditions? After a thorough predictable and consistent than that of chestnut species will continue to provide review of the published information and seedlings. However, with chestnuts the an important nut crop worldwide. available sources for chestnuts by Cornell situation is more complicated than with As fruit growers in the Northeast graduate student Miranda Kahn, we other fruit and nut species. One of these look for alternative crops for profitable selected six that appeared to be complications is that grafted chestnut niche markets, there has been renewed well suited to our climate in Upstate NY, trees cost much more than seedlings interest in chestnuts. Domestic and were available both as grafted and (about $20 vs. $3 per tree). Also, in the production in the US is small, and most seedling trees. The six commercially US there have been problems with de- of our $20 million annual market demand available chestnut cultivars, included layed graft incompatibility in chestnuts is met by chestnuts imported from China, ‘Mossbarger’ (Castanea mollissima), that causes stunting or death of grafted Korea, and Europe. Growers are planting ‘Douglas 1A’ (C. mollissima X dentata), trees during their early years in the or- chestnuts from the Southeast to the ‘Eaton’ (C. mollissima X (crenata X chard. This problem may be caused by Pacific Northwest, and there are several dentata)), ‘Skioka’ (C. mollissima X sativa), genetic incompatibilities between seed- chestnut in the Finger Lakes and ‘Layeroka’ (an open pollinated seedling ling rootstocks and some chestnut culti- Hudson Valley regions of NY. Besides a of ‘Skioka’), and ‘Grimo 142Q’ (an open vars. It could also result from improper potential cash crop to market, chestnut pollinated seedling of ‘Layeroka’). These grafting techniques that are complicated growers can expect other less tangible cultivars and their seedling progeny were by the vascular anatomy of chestnut benefits as well. Nut trees require fewer chosen because they represented a twigs, which develop cambium in dis- inputs than most other , and can be sample of commercially available crete arched units rather than a simple grown in pastures or woodlots that might cultivars thought to have enough cold circle around the stem. There are also otherwise not produce a marketable crop. tolerance and blight resistance to survive unanswered questions about the relative Chestnut wood is highly resistant to in our region. They were also available vigor of grafted vs. seedling chestnuts decay and can be used instead of pressure in adequate numbers of both grafted and that need to be answered in order to de- treated pine for fence posts and similar seedling trees, a requirement for meeting termine the optimum tree spacing that purposes. Other benefits are enjoyed by our other objectives of comparing grafted will allow enough row space for each tree those who plant a small grove of and seedling tree performance, and in the mature planting.

NEW YORK FRUIT QUARTERLY • VOLUME 13 NUMBER 1 • 2005 33 To evaluate the trade-offs between bloom in early July upon current year 70 grafted planting costs and tree performance of . Considering how late in the 60 seedling grafted vs. seedling chestnuts in our season they begin to develop with our 50 experiment, we obtained trees of six short growing season in the Northeast, 40 cultivars that were grafted onto their own chestnut varieties that mature too late in 30 seedling rootstocks (to avoid genetic autumn may be damaged by frost before incompatibility). At the same time, we their nuts mature. A lake-moderated site spr95-99 TCA 20 obtained seedling trees grown from these that extends the frost-free season will be 10 six cultivars. By comparing the beneficial for chestnuts, as for 0 performance of grafted cultivars with or late ripening like Eaon that of seedling trees grown from nuts of ‘GoldRush,’ ‘Cameo’ and ‘Fuji.’ Skioka each grafted clone, we hoped to learn How should chestnut trees be Layeroka Mossbarger Grimo 142Q which of these six cultivars performed managed? Another important Douglass 1A best in NY, which of them had problems management question for chestnuts, Figure 1. Cumulative increase in cross- with graft incompatibility, and whether and training system, is also one sectional area (cm2) of six chestnut varieties as some of the cultivars could produce of the least studied. Chestnuts bear on grafted or seedling trees, during five years of seedling trees of comparable horticultural flowering laterals that develop in axillary growth after planting in 1995. Values are means of five replications ± SE of means. quality to their parents. buds on vigorous growth from the Another objective of our study was previous year; so mature trees usually insect control consisted of glyphosate to estimate the extent to which important fruit mostly in the outer canopy margins. herbicide applications in the tree row horticultural traits in chestnut are passed Hence the most productive part of during May and July, and carbaryl on from parent cultivars to their seedling mature chestnut trees is usually an outer insecticide applications during June and progeny. Geneticists call this layer of the canopy, surrounding an July. Trees were drip-irrigated as needed. characteristic “heritability.” Cultivars unproductive inner tree volume. Pruning with high heritability can impart many and training systems that increase light Results of their desirable horticultural traits to penetration into the canopy might their offspring, and are excellent increase the proportion of productive Cumulative tree growth and candidates for selective breeding. They wood in chestnut trees. By forming a mortality. During five years of are also “good parents” that are likely to smaller more open-center tree, such a observations, tree growth was not produce seedling trees with the desirable training system could also improve pest significantly different among the grafted traits of their parents—such as yield control efficacy. In this study, we cultivars, but among the seedling precocity and efficiency, good nut size evaluated two pruning/training tree- lineages, trees of ‘Douglas1A,’ ‘Layeroka’ and quality, disease and cold resistance. forms—open center, and central leader— and ‘Skioka’ were smaller than the others Knowledge about the heritability of for five years during establishment of the (Figure 1). Average trunk cross-sectional chestnut traits thus has practical planting. We also monitored insect pests area was about twice as great for seedling implications for nut growers trying to and diseases to determine whether they trees compared with their grafted decide whether it is worth making the could be adequately controlled. parents, and this trend was consistent for extra investment in grafted trees. If some Our experiment enabled us to make all lineages except ‘Skioka.’ There were chestnut varieties reliably produce open- comparisons between grafted and also major differences in cumulative tree pollinated seedlings that closely resemble seedling trees, among grafted varieties, mortality among the cultivars and their their mother tree, then growers could among seedling varieties, and among seedlings (Figure 2). The lowest mortality save money and avoid graft pruning/training systems across rates after five years were for seedlings incompatibility problems by planting varieties. We collected data on the of ‘Eaton’ and ‘Grimo 142Q’ (both 4%), inexpensive seedling trees from parent following traits: 1) dates of bud break, while the most tree losses occurred for varieties that have demonstrated high bloom, fruit set, and nut ripening for each grafted ‘Skioka’ (71%) and its seedlings levels of heritability for essential variety; 2) tree age at first flowering and (40%). For ‘Douglas 1A,’ ‘Eaton,’ ‘Grimo horticultural traits. fruiting; 3) productivity (number and size 142Q,’ Mossbarger,’ and ‘Skioka,’ the Where can chestnuts be grown in of nuts); 4) consistency of bearing from mortality rates were two to three times the Northeast? We located the study at year to year; 5) tree mortality and damage greater for grafted cultivars compared a Cornell research farm near Lansing NY from winter cold, insects and pathogens; with their seedling progeny. that provided favorable conditions for and 6) tree vigor and form. Nutritional Nut yields and quality. The grafted chestnuts—a somewhat acid soil, good status and fertilizer responses were trees all produced some nuts in the soil and air drainage, a moderating assessed by analysis. The trees were second and third years after planting Cayuga Lake effect, and southwest facing obtained from commercial nurseries and (1996-97), while seedling lineages slopes. Previous research by Miranda planted by hand in mid-April 1995, in produced only a few nuts in those early Kahn with seedlings in controlled north-south rows on a west-facing slope years. From the fourth year onward, both environment growth chambers had close to Cayuga Lake. Tree spacing was grafted and seedling trees have produced shown that chestnuts would grow and eight meters (26.2 ft) between rows and a marketable crop of nuts annually. produce best in sites with about 3000 three meters (9.8 ft) within rows. Deer Surprisingly, seedlings of ‘Grimo 142Q’ Growing Degree Days (GDD base 50°F); protection was provided by a high fence produced more nuts per tree than their so good exposure to afternoon sun and around the , and trees had grafted parent cultivar. In general, the heat are important for this crop in our mesh trunk guards to protect them from cultivars that were more productive as region. Chestnuts bear on flowers that meadow voles and rabbits. Weed and grafted trees—such as ‘Mossbarger,’ 34 NEW YORK STATE HORTICULTURAL SOCIETY 90 4000 80 grafted 3500 grafted seedling seedling 70 3000 60 2500 50 2000 40 1500

% Mortality ‘99 30 Cum. Yield (g) Cum. Yield 20 1000 10 500 0 0 Eaon Eaon Skioka Skioka Layeroka Layeroka Mossbarger Mossbarger Grimo 142Q Grimo 142Q Douglass 1A Douglass 1A

Figure 2. Cumulative mortality (percent) of grafted Figure 3. Cumulative yields (average grams of nuts Figure 4. As chestnuts ripen, they expand rapidly and seedling chestnut trees of six varieties, after per tree, dried to 15% moisture content) of six and burst open the protective burr that surrounds five years growth. Values are means of five grafted and seedling chestnut varieties during the them during summer as they develop. Each burr replications ± SE of mean. first five years of growth. Values are means of five usually contains three nuts, but only one or two of replications ± SE or mean. them develop to maturity. These chestnuts are ready to harvest. ‘Layeroka,’ Grimo 142Q’ and ‘Eaton’— of yield and nut quality than their were also relatively productive as seedlings for the variables that we seedling trees. Heritability of the early measured. Considering the higher costs yielding trait in these cultivars appeared and greater mortality of grafted trees center. In contrast, open-center pruning to be quite high. Considering the during establishment years, there and training of the more vigorous cumulative yields of grafted and seedling appears to be little financial reward that seedling trees produced an overly dense trees for each cultivar, dry-weight nut would justify the greater costs and risks and shaded central area, while seedling production was greatest for seedlings of of planting grafted chestnuts—if growers trees developed a reasonably good ‘Grimo 142Q’ and grafted trees of can obtain seedling trees of varieties such pyramid form that benefited from apical ‘Layeroka’ (Figure 3). Yields were as ‘Eaton,’ ‘Layeroka’ or ‘Grimo 142Q’ dominance after five years of central- equivalent for seedlings vs. grafted trees that performed reliably as seedling trees. leader pruning and spreading. of ‘Eaton’ and ‘Skioka,’ and relatively low Some of the differences within these A few general comments about but greater for grafted trees of ‘Douglas chestnut lineages were surprising. For chestnuts may be useful in concluding 1A’ and ‘Mossbarger.’ Yield efficiency example, ‘Skioka’ was the worst this report. With respect to marketing, the (nut yields per unit of trunk cross- performing variety, while its daughter demand for chestnuts is mostly among sectional area) was several times greater ‘Layeroka’ was among the most immigrants from Asia and Europe, who for all of the grafted cultivars compared productive. We were also surprised at the live in major metropolitan areas of the US. with their more vigorous seedlings (data yield precocity of all these cultivars and Growers should develop a marketing not shown), even though total yields per seedling trees, most of which produced plan to reach these customers before tree were actually less for some grafted nuts in the second or third year after investing in a chestnut orchard. We were cultivars (Figure 3). Average size and dry planting. able to sell all of the chestnuts from our weight per nut were slightly greater (4 For grafted trees, planting density experiment for $3 per pound at a Cornell vs. 6 g dry weight per nut) on grafted vs. could probably be increased by closer Horticulture Department’s retail produce seedling trees in the early bearing years. spacing than our 3 by 8 meter grid for market that serves a diverse consumer However, by the fourth and fifth years the trees in this experiment. Most of the base, but many of our local customers average nut weights were statistically grafted trees have barely filled their needed instruction in how to prepare similar for grafted and seedling trees, allotted space in the tree rows at the time chestnuts for cooking. ranging from 8 to 12 g dry weight per nut. of this report, ten years after they were As our planting matured, a resident Nut size was somewhat greater on the planted. A problem with higher planting population of the chestnut-oak curculio lower yielding cultivars (e.g. ‘Douglas densities for grafted chestnuts would be weevil developed. This pest is native in 1A’) and reduced on the heavier yielding that sprouts almost always oak acorns and fed on the American trees. The values recorded for nut yields replaced grafted trees that died, and those chestnut before it was decimated by were for nuts dried to about 15% seedlings would soon overshadow the blight. The chestnut weevil has a long moisture content, to correct for surrounding grafted trees. For seedling snout and ovipositor that enable it to differences in fresh weight values caused orchards, a planting distance of 6 by 10 puncture the thick spiny integument or by rainfall during harvest time. Fresh meters would be appropriate, as these “burr” that protects developing weight values for nuts were about four trees became too crowded at the 3 by 8 chestnuts. It deposits eggs in the interior times greater than dry weights, so the meter spacing in this experiment. nutmeat, where they hatch in August and values in Figure 3 can be multiplied by a Responses to pruning and training partially consume the nutmeat before factor or four to estimate marketable fresh systems also differed for grafted vs. over-wintering as inactive larvae. It is weight nut production per tree. seedling trees. The less vigorous grafted difficult to detect curculio egg-laying damage in harvested chestnuts, and some Discussion trees responded quite well to open-center training, developing multiple scaffolds of our customers were not pleased when Grafted cultivars generally did not with relatively wide branch angles and they spent a considerable time peeling provide more uniformity or consistency adequate light maintained in the tree and preparing chestnuts, only to discover NEW YORK FRUIT QUARTERLY • VOLUME 13 NUMBER 1 • 2005 35 weevils inside some of them! Several containers under refrigeration. der NY growing conditions, and wheth- well-timed insecticide sprays during Alternatively, they can be dried down to er it was more economical to grow inex- July and early August may be required about 15% moisture content in a pensive seedling trees or more expensive to control this pest in established dehydrator or spread out in trays on a grafted trees of known chestnut culti- chestnut orchards. Other than occasional greenhouse bench. Dried chestnuts can vars. We began the experiment in 1995, European red mite flare-ups and gypsy be stored for months in airtight bags planting six clonal (grafted) cultivars, moth infestations during some years, under refrigeration, but they must be and six groups of seedling trees grown there were no serious insect or disease boiled and rehydrated before they can from nuts of each grafted cultivar. We problems with our planting during this be consumed or used in most recipes. compared a number of different traits experiment. There are many economic and hor- among the six varieties and their seed- Perhaps the greatest challenge in ticultural challenges to growing chest- lings, including: 1) tree age at first bear- growing chestnuts is harvesting your nuts in the US, Growers interested in a ing, 2) nut production and quality, 3) nuts before the squirrels, woodchucks, niche market fruit crop with a long his- cold hardiness and tree survival, 4) pest raccoons, foxes, coyotes, deer, feral hogs, tory in our region, a high market value, problems, and 5) tree vigor and form. or bears get them! Squirrels are the most and many delicious uses ranging from The grafted trees began fruiting in the difficult wildlife pest to control, as they traditional turkey stuffing, to bread, second year and produced more nuts per climb trees and sever the stems of almost cookies or elaborate French pastries, or unit of trunk cross-sectional area (high- mature chestnut burrs, returning later to just those nostalgic “chestnuts roasting er yield efficiencies). They suffered extract the nuts when the fallen burrs on an open fire,” might consider chest- greater mortality during the first five have opened on the ground. The other nuts. There are some good chestnut va- years, however, up to 70% losses for one pests can be managed if you harvest nuts rieties available from commercial nurs- cultivar (‘Skioka’), compared with less every few days over the one to two week eries. They establish quickly and pro- than 10% mortality rates for most of the period between late September and mid duce well in a good orchard site, grown seedling lineages. Cumulative yields per October when most chestnut varieties either as grafted trees or seedlings of tree were best for ‘Eaton,’ seedlings of reach harvestable maturity in NY. several varieties. ‘Grimo 142Q,’ and grafted trees of ‘Lay- Chestnuts increase rapidly in size and eroka.’ Nut size and quality were simi- change color from creamy white to light Further Reading lar for grafted cultivars and their seed- brown as harvest time approaches, ling progeny, and the seedlings came carbohydrates convert to soluble solids The Northern Nutgrowers Associa- into production a year later than their and the nuts absorb water and fill out tion meets annually in the region and grafted parent trees. Chestnut curculio (Figure 4). During this maturation phase publishes an informative newsletter and weevil was the main pest problem, al- the nuts burst open their protective proceedings of their meetings. Dr. San- though wildlife such as squirrels, wood- spiny covering, and within a week or so dra Anagrostakis (Sandra.Anagnostakis chucks and deer could also be a prob- the mature nuts will drop to the ground. @po.state.ct.us) is a chestnut expert and lem unless the nuts are harvested before There is a brief window of opportunity breeder at the Connecticut Agricultural they fall to the ground. Grafted trees re- at this time, when a picker with sturdy Experiment Station, and has many use- sponded well to open-center pruning gloves can pull off or shake down the ful scientific and general-interest publi- and training, while the seedling trees opening chestnut burrs and extract the cations about chestnuts available by re- were easier to manage as central leader one to three nuts that each contains. quest. Greg Miller is a chestnut breeder trees. Grafted trees were about 40% Once those nuts pop out of the open and owner of the Empire Chestnut Com- smaller than their seedling progeny af- burrs and fall on the ground, they are pany and nursery in Carrollton, OH. His ter 10 years. We concluded that growers difficult to find. They may also become webpage (www.empirechestnut.com) could successfully produce chestnuts in soiled, water soaked and more prone to has excellent information and other links upstate NY regions with lake-moderat- mold in storage, and are soon devoured to relevant sites and sources for chest- ed climates. Inexpensive and hardy by appreciative local wildlife. nut growers. The standard textbook for seedlings of chestnut cultivars such as Researchers in Michigan have tested chestnuts and other nut trees (the Hand- ‘Grimo 142Q,’ ‘Eaton,’ ‘Layeroka,’ or pre-harvest Ethephon treatments and book of North American Nut Trees, pub- ‘Mossbarger’ may be more economical cherry-tree shakers as mechanical lished by R. Jaynes in 1969) is out of print than, and equally productive as grafted methods for harvesting chestnuts, with but still available in many libraries. Sev- trees under our growing conditions. encouraging results. For tart cherry eral dozen commercial nurseries sell Harvesting chestnuts is very labor inten- growers with the necessary equipment, grafted or seedling chestnut trees, and a sive, and marketing them will require growing chestnuts could be an option for quick Google search will yield their con- careful development of a niche custom- niche markets. Otherwise, harvest labor tact information and catalogs. er base in major metropolitan areas of could be a prohibitive part of production the Northeast. costs—especially if northeastern Summary growers are competing with chestnut growers in China to serve the relatively In this project we investigated some Ian Merwin is a research and teaching pro- limited US market for this crop. practical questions about edible chestnut fessor in the Department of Horticulture in For long-term storage, chestnuts can production in New York. Specifically, we Ithaca, NY. Miranda Kahn was a graduate be disinfested with a dilute Clorox wanted to know which chestnut variet- student and Rachel Byard a technician in solution, and stored in airtight ies or lineages would perform best un- the Department of Horticulture.

36 NEW YORK STATE HORTICULTURAL SOCIETY