Castanea: Staple Food Crops do Grow on Trees
Contents of Article:
What a Yield
The Chestnut in World History
The Botany of Castanea
Site and Soil Basics
Disease and Pests
Seed Starting and Propagation
A Few More Castanea Cranks
Castanea Tree Species Info
“The greatest tree food crop of the world—the chestnut—is not grown within the United States, except very little. We can grow it. We will some day. It is a crop that would pay on out eastern hill farms. It would change much of our so-called “marginal land” from unprofitable to profitable farming land. Just now only a few people, regarded as cranks, are trying to grow it.”
-Carroll D. Bush, Nut Grower’s Handbook, 1946
These words were published within months of World War II coming to an end. Imagine if all the human energy that went into that era’s “victory gardens” and domestic reorganization of society was then used to create groves of chestnut trees integrated into forest gardens and agro-forestry plots. Dare I say we would have found our way back to the Garden of Eden by now? The World War II mobilization metaphor has been used time and again to stress the need for urgent social change on a massive scale. From peak oil and climate change to overpopulation and global food scarcity it’s pretty clear by now that we can’t go another 65 years living the pretense of the industrial growth narrative. I’m not sure how severe, or how soon, the consequences of that narrative will come to fruition, but I am certain of one thing: throughout the temperate climate world the chestnut is one of the most choice plant species for creating permaculture systems that will allow human cultures to transition to a regenerative post-industrial livelihood.
What a Yield:
Let’s start simply by looking at the numbers to put the potential yields in context. Chestnut trees can produce up to 2 tons of nuts per acre—that’s 4,000 pounds! That out produces average U.S. wheat production at 1,800-3,000 pounds of grains per acre—not to mention you can’t create a medicinal and edible under-story in a wheat field. As far as nut trees go, chestnuts can start bearing nuts relatively early on as well. Depending on the species, variety and care of the tree, most trees will start producing between four or five years of age. Some Japanese varieties can produce seed as early as their second year. By year ten, chestnut trees can yield 55-110 pounds per tree, and Chinese chestnuts yield 150-300 pounds per tree once mature. The largest yielding chestnut tree ever recorded produced over 1,100 pounds of nuts in one season. Staple food crop? There is a reason why the chestnut has been called “the bread tree” in Europe for hundreds of years, and why the Romans called the chestnut “the acorn of Zeus.”
The Chestnut in World History:
The chestnut has been an important food crop to ancient societies and indigenous cultures throughout the world, and has been the only temperate tree to serve as a significant human staple food (except maybe oaks on occasion, which are in the same family). In Japan, archeological sites from 8000 BC reveal evidence of centralized processing and consumption of the nuts, and the Japanese have been breeding the Japanese chestnuts (Castanea crenata) for over a thousand years. China, who is today the world’s largest commercial chestnut producer, also has a rich chestnut orchard tradition dating back to at least three thousand years ago. The Chinese chestnut (Castanea mollissima) has the largest native range and the Chinese have the oldest recorded cultural practices in the world.
The Europeans began breeding the trees (Castanea sativa) during the classical era of ancient Greece, and the tree was spread far and wide by the Romans, who not only ate the nuts, but also used the timber of the trees for creating vineyards. Chestnuts also found their way into the stories and mythologies of the time. In Greek mythology, Artemis, the goddess of the forests and chase, escaped Zeus by shape shifting into a chestnut tree and hiding in the forest. In the mountainous regions of Italy there is a folk tradition of telling children that babies come from chestnuts. During the Middle Ages, a mountain culture in present day Italy had a liturgical calendar that began with the chestnuts flowering, and in the literature of the time, one can find frequent references to the castagnatores—skilled horticulturalists who specialized in farming chestnuts in the hillsides. Chestnuts even had their place in fighting fascism. As the guerilla armies of Spain would retreat into the forests, there are accounts of local farmer’s supporting the resistance by sharing their nut groves with the anti-fascist soldiers.
The significance of the American chestnut (Castanea dentata) in native forest ecosystems can hardly be exaggerated. It was one of the most dominant canopy species in eastern forests. Many ecologists believe that 25% of the trees in western North Carolina were once chestnuts. The chestnut tree was a significant member of many eastern forest communities, including: the northern hardwoods, pine-oak-heath communities, Appalachian rich coves, oak-hickory forests, piedmont river bluff forests, and was once the co-dominant species in both the high-elevation red oak and low-elevation chestnut oak forest communities. The chestnuts were by far the best and most reliable nut for wildlife, including turkey, black bear, raccoons, deer, squirrels and passenger pigeons. The accounts of the devastating affects the chestnut blight had on eastern wildlife are innumerable. The trees were an important part of the forest phosphorus cycle, as the passenger pigeons would eat them during migrations and drop their fertilizer on the land below. They were also important in soil development through dropping their nitrogen and potassium rich leaves into the forest litter. The leaves can recycle 24 pounds of nitrogen and 10 pounds of potassium per acre.
Being such a central member of native forests the tree was undoubtedly also very important to the native peoples who lived in the trees range. There is reasonable speculation that native peoples even expanded the range of the chestnut, like they did with the paw paw and black walnut. The chestnut provided them with food, hunting grounds, shelter, bark tanning, and medicine. The Cherokee used the leaves to treat heart ailments, sores, coughing, and typhoid; and they used the bark to stop bleeding after birth. Like in Europe, the chestnut made it’s way into indigenous mythologies. There are many native stories from the Iroquois territory in New England down to Natchez lands in Louisiana that revolve around the chestnut. To peoples whose subsistence was so intricately connected to the rich native forests of the east, it’s really hard to comprehend how important the chestnut must have been to the natives of North America.
The settlers from the Old World also certainly found the chestnut to be an extremely important part of settling eastern North America. The rot-resistant chestnut wood was practically used for everything associated with building, including timber framing, and making shingles and fence posts. The nuts were used as fodder to run their hogs and other animals on. I have personally talked to old-timers in North Carolina who remember their grandparents talking about how the hogs and black bears didn’t taste as good after the chestnuts died. Like the natives, they also used the tree for medicine, food and bark tanning. The nuts were also harvested and used as supplemental income for many mountain folk who would sell the nuts to nearby cities in the fall. In Appalachia there was a tradition of “the chestnut commons,” where a stand of forest would be thinned and maintained with chestnuts in order to have communal grounds for harvesting and running animals on during the fall mast production. This practice was particularly beneficial to slaves, sharecroppers, and the poor who didn’t possess enough land to support their animals.
In North America the reign of the chestnut ended—at least for now—in 1904, when the chestnut blight was found in the NY city zoo. It spread in less than one generation, and by 1940 it had virtually wiped out all the chestnut trees in their native range, leaving only stump sprouts and one of the biggest disturbances to eastern forests in recent history.
The Botany of Castanea:
The genus castanea includes the four tree species(American, European, Chinese, Japanese), as well as several shrubs from Asia and North America, including the Allegheny chinkapin (C. pumilla). Castanea is a member of the family Fagaceae, which includes the oaks and beeches; the family has over 600 species in 6 genera around the world.
Chestnut flowers bloom about two months after their spring growth begins. I’ve read accounts of how some folks in Appalachia would describe the chestnut flowering season as “the whitening” because the hillsides in early summer would be absolutely covered with chestnuts flowers. Like most nut trees, they are monoecious, meaning the male and female flowers are on the same tree, but they are in separate flowers. Their catkins can be seen long before their flowering stage, and even though they flower relatively late in the season, the immature catkins can be damaged by frost.
They have two types of catkins. The unisexual catkins at the base of the new seasons shoot produce staminate (male) flowers and pollen, while the bisexual catkins, toward the tip of the shoot produces pistillate (female) flowers and eventually burs. This organization is one reason why chestnut trees must get a good amount of light if the tree is to produce lots of flowers. The branch tips that have more vigorous growth are more likely to produce a lot of female flowers. As the shoot continues to grow beyond the catkin-bearing area, they form vegetative buds in the leaf axils, which contain next year’s flower buds. The trees also have a natural plan B mechanism. Not all buds break with the first flush, so if a late frost does happen to damage the buds, there is a reserve set of insurance buds that will allow the tree to still produce some nuts. Thus light, along with water and soil fertility, is important to achieve vigorous shoot growth with lots of flowering buds.
Flowering begins with staminate flowers shedding their pollen, and a within a few days pistillate flowers open and become receptive. During the latter period of the pistillate receptivity the bisexual flowers open and begin shedding more pollen. Even though the pollen-shed period is longer than the receptivity period and they may overlap somewhat, chestnuts are not generally considered self-fertile and cross-pollination is strongly recommended. The trees are wind-pollinated, but their pollination is greatly increased with the help of insects, so having beehives or healthy native pollinator habitat nearby greatly increases the yield of nuts on the trees. Warm, dry, windy days are best for good wind pollination, but bees, butterflies and beetles all help, especially when the weather isn’t ideal for wind pollination. And chestnut honey is also a delicious much sought after product in many places. In order to achieve good pollination you don’t want to have all clones of one tree, and you don’t want the trees to be spaced at more than 30 meters apart from each other.
From flowering to nut ripening takes about ten weeks or longer. The last two weeks are vital as the nut kernels put on half of their mature weigh in that brief period. A lack of wind protection can lead to strong fall winds knocking off prematurely developed nuts, and drought or cold weather can lead to a decrease of growth in the critical last weeks. A single tree can drop nuts from a period of a few days to two or more weeks, and one can usually harvest nuts for 4-6 weeks on various trees in the same area.
Growing & Caring for Chestnut Trees:
If you are planning on establishing some chestnut trees on your permaculture site, or in your forest garden or orchard, there are some basic things you should know about how to grow and care for them.
Site and Soil Basics:
They like well-draining, slightly acidic soils (pH 5.5-6.5). They are fairly drought tolerant once established, but like moist places as long as they are not placed in waterlogged soils. They can be problematic with heavy clays or limestone soils. Sloping ground is good for water and air drainage and generally keeping them out of frost pockets is a good idea. They like winter chill hours that range from 450-650 hours, and can be very cold tolerant once fully dormant. Like most nut trees they are tap-rooted, thus they are not favorable to being transplanted. In places with very hot summers they will tolerate some partial shade. They are generally planted 40 feet apart, but it is not an uncommon practice to plant them closer together and thin some out at a later time. This can be a great way to start a seedling nursery, and then once the trees you’ve selected to remove are thinned out you can plant nitrogen fixers or other edible plants in between your established chestnuts.
After planting chestnuts you’ll want to encourage root growth to get the tree off to a healthy start. Remember, the trees are tap-rooted so they are not particularly happy when they are transplanted. Think long and hard about where you’ll want to put them and try to keep them in that location. The only fertilizer I’d use the first year is one that promotes root growth. Water the trees in well and irrigate them if possible and necessary. Mulching around the tress to suppress weeds and hold water is a good idea, but keep the mulch off the trunk to protect the trees from critters that might girdle the trunks. In hot regions you might want to whitewash trunks to protect them from the sun.
How you prune the trees might vary depending upon what species and varieties you have, and what circumstances in which you are trying to grow them. Traditional orchard trees are pruned with an open-vase method. The contemporary Italian/French method of pruning for European and European hybrids is to create an upright pyramidal structure with a central leader, but this is a strategy for commercial production aimed at maximizing yields through increasing tree density. You might want to look into this method if your permaculture site is small and dense or you are trying to maximize production space. The Asian species will want to spread out, so it is best to give them as much space as you can spare. Pruning is best to do in the early summer when it is hot and dry to minimize the chance of infection. You can prune saplings by pinching buds to encourage a good whip and upright growth pattern; this will be helpful in getting the trees out of the range of deer a.s.a.p. Generally, once your trees are established pruning should be minimal unless you are trying to fit it into a space with a particular arrangement in mind.
It is best to fertilize in early spring to encourage vigorous shoot growth. You should not fertilize with lots of nitrogen the first year for fear of fertilizer burn, but it is a good idea to water with a seaweed solution or another amendment that aids with after-planting or transplant shock. Nitrogen shortage can lead to a lack of vigor and poor seed production, while excess nitrogen can lead to small nuts, an increased chance in getting anthracnose, and a delay in tree maturity. An easy general rule to follow is fertilizing with 1 pound of organic 5-10-5 for every year of growth on a vigorous tree, or every inch of tree trunk diameter on less vigorous trees. Martin Crawford, director of the Agroforestry Research Trust, has a very informative pamphlet on chestnuts that covers various fertilizer strategies using different organic fertilizers. He also mentions inter-cropping nitrogen-fixing plants like Elaeagnus spp. and Italian alder with chestnuts at a ratio of 33% nitrogen-fixers with 66% chestnuts.
I am currently setting up a similar system on an Appalachian homestead, using goumi and black locust as my nitrogen-fixers. For inhabitants of North America, black locust is an ideal candidate that has a thin canopy and good coppicing function. Comfrey mulch or compost tea is an easy way to feed your trees potassium. Crawford also explains a comfrey mulching system in which each chestnut has 5 or 6 comfrey plants to meet its K needs.
Disease and Pests:
There are a few pests and diseases to be aware of when growing chestnuts. Anyone who has ever harvested them has probably come across chestnut weevils. They lay their eggs in developing nuts, eat their way out, and over-winter in the leaf litter. A good way to decrease their numbers is to run poultry under your trees. You can also treat the nuts by giving them a water bath at 120 F for 20 minutes; this should kill the weevils and leave the seeds viable.
Oriental Gall Wasp is another problem currently spreading around the southeast. The wasps lay their eggs in the tree buds and developing larvae cause the shoots to become stunted. The Japanese chestnut is the most resistant species, and there is currently research being done in both Asia and North America using natural control methods. For many people, the biggest problem with attempting to establish trees will be deer. I have witnessed deer in the winter eating every chestnut in a stand of dozens back to the ground—every single one! Tree guards, fences, vigorous growth, dogs, shooting and eating them, whatever it takes, protect your trees from deer.
Ink disease is a root rot fungus that has been a problem in Europe and killed off many of the American chestnuts in their southernmost range during the late 1800’s. The fungus attacks the root bark, starting at the smallest feeder roots and eventually works its way to the base of the trunk. It causes the roots to stop growing, crack open, and release a sap that turns black from oxidation of the tannins. It is not necessarily fatal and Japanese chestnuts and Japanese hybrids are resistant. Preventive measures include: Planting trees in well-draining soil and inoculating seedlings with mycorhizal fungi of the Basiomycetes group, like Leucopaxillus cerealis.
Chestnut blight has been by far the most devastating problem the trees have come across. As mentioned above, the fungal blight has nearly eradicated the American chestnut, and has done considerable damage to the European. It attacks the trees via wounds on branches, works its way under the bark, secretes toxins, and causes the cambium cells to collapse, eventually killing the trunk. In Mycellium Running, Paul Staments makes a very brief mention of hearing about a Canadian nurseryman treating it using the chaga mushroom. In Europe, blight infected trees are treated with hypo-virulent strains of the blight that dominate the deadly strain and allow the trees to form a barrier of cells to defend themselves.
The American Chestnut Foundation has been crossing the American with the Chinese chestnut trying to create a blight resistant American chestnut tree to use in reforestation projects. They are having good results with their latest BC3F3 hybrid, which is very similar to the American genetics and displaying good blight resistance so far. For now, planting Chinese and hybrid chestnuts is your best bet for avoiding blight problems.
Seed Starting and Propagation:
Staring chestnut trees from seed isn’t difficult, but there are a few things you can do to make sure your attempt if effective. Collect the seeds as soon as they fall from the tree because they can lose viability from drying out quickly or becoming damaged by weevils. Soak them for two days in water before you stratify them. If you are worried about weevils process them with a warm water bath, as mentioned above. They need to be cold stratified for 1-3 months between 32-36 F. Make sure they don’t freeze, dry out, mold or rot. You can store them in the refrigerator or another temperature controlled space in peat moss or any other medium that keeps them moderately moist. You can sow them directly in the ground in the fall, but you might want to put hardware cloth around them because animals will want to eat them. Also, it’s not a bad idea to mulch them to keep them from freezing and thawing during the winter. Plant the nut at a depth of 5 cm. Place it on its side, not right side up; this will help them germinate with straight growth and preserves energy. The ideal germination temperature is 69 F at night and 86 F during the day. They should come up in 1 month. Larger seeds make more vigorous seedlings.
There are many chestnut varieties that have been selected and breed for various traits. The most common of these, of course, is nut size, but disease resistance, growth structure, pollination, and flavor are also all reasons people want specific varieties of trees. Grafting and mound layering are the techniques used to propagate chestnuts in a vegetative manner. Chestnuts have pretty severe grafting incompatibility issues, meaning that you can’t just take any chestnut, graft it on to another as a rootstock, and expect it to take. The Northern Nut Growers Association has some helpful research on chestnut graft compatibility, but the most common, reliable and easiest practice is simply to graft cuttings from a mother tree onto it’s own seedling. The chances are very high that the seedling will be different from its parent, but they are also very good that your grafts will form a strong long-term union when done this way. It is recommended to graft once the rootstock had fully leafed out, between mid-spring and mid-summer. Have your scion stored to keep it dormant, and attempt to graft it on a warm dry evening. You may want to cut the rootstock a day or two in advance because it is possible the tree will initially bleed sap and ruin the graft take. Chestnuts can be grafted using the whip & tongue, splice, or kerf grafts, and they can also be top-worked by T and chip budding in the late summer or early fall.
A Few More Castanea Cranks :
Today there are definitely more people involved in growing chestnuts than there were in 1946 when Carroll Bush published the Nut Grower’s Handbook, but we could always use a few more chestnut “cranks,” especially in the cutting edge world of permaculture and agro-forestry. The American Chestnut Foundation is currently selling their most recent American hybrids, and has set up a program to plant the tree on voluntary experimental orchards for those private landowners who have the space and interest. There have now been several generations of scientists, hobbyists, nursery people, growers, and others who have been working with the chestnut. They have found improved ways to grow them, selected and breed new varieties, created organizations to share knowledge and practices, and promoted the value of the chestnut all over the temperate climate world. The tree—maybe more than any other—has a definite role to play in our future in promoting wildlife habitat, forest restoration, climate change adaptation, experimental forest gardens, public edible plantings, and as a staple food crop that can feed not only our stomachs, but our hearts and connection to the more-than-human-world.
Castanea Tree Species:
What You Need To Now About The Various Chestnut Trees
Listed below are the 4 chestnut tree species and relevant information, including their height, growth habit, nut sizes, hardiness, disease factors and nutritional differences.
American (Castanea dentata)
Height: 40 m
Growth Habit: Upright with central leader; good canopy
Size of Nuts: 4-5 grams (75-150 per lb)
Hardiness: Zone 5 (even 4)
Bud Break: Late
Disease Factors: Blight susceptible
Nutrition: Carbs: 40%, Protein: 10-11%, Fat: 7-11%, Fiber: 19%
European (C. sativa)
Height: 30 m
Growth Habit: Upright with central leader; good canopy
Size of Nut: 10-25 grams
Hardiness: Zone 6
Disease Factors: Ink disease & moderately blight susceptible (HV strains)
Nutrition: Carbs: 66%, Protein: 6%, Fat: 4%, Fiber: 14%
Chinese (C. mollissima)
Height: 12-20 m
Growth Factor: Sprawling with large branches; no central leader
Size of Nut: 5-25 grams
Hardiness: Zone 5
Bud Break: Early
Disease Factors; Blight resistant; Various resistance to ink disease & gall wasp
Nutrition: Carbs: 65%, Protein: 8%, Fat: 2%, Fiber: 14%
Japanese (C. crenata)
Height: 9-15 m
Growth Habit: Lack central leader; often multi-stemmed
Size of Nut: 30 grams per nut (largest)
Hardiness: Zone 6
Disease Factor: Resistant to ink disease & mostly resistant to blight
Nutrition: Carbs: 90%, Protein: 10%, Fat: 0.4%, Fiber: 14%
All chestnuts also contain good levels of vitamin C, copper, manganese, folates, thiamine, & B6