Chestnut: The Bread Tree, Part 3 of 4
Chestnuts are not difficult to grow. They are easy to propagate from seed and will often begin bearing in just 3-5 years (though American chestnuts take 8-10 years). Chestnuts are primarily wind pollinated, monoecious trees (each tree produces male and female flowers). They do not pollinate themselves, so two or more should be planted less than 50 feet apart.
Chestnut trees have a moderate to fast growth rate, similar to that of red maples. Of course, this depends on soil and tree health. They prefer good drainage and an acid pH, but this does not always have to be the case.
I have seen wild American chestnuts growing in low lying swampy areas. At first glance, it seems that they can tolerate wet feet, but a closer look at the topography reveals something else. In older forests the ground is very uneven. As large trees topple over and are uprooted, a depression is created where the root mass once was. As the root ball breaks down, a mound is formed. This landscape feature is referred to as ‘pit and mound’ or ‘pillows and cradles’. It is commonly associated with almost all old growth forests.
Pit and mound landscapes are essentially covered with vernal pools and raised beds. Chestnuts, like almost all trees, prefer to grow on the mounds. If you have a wet field, and want to grow chestnuts or really any other fruit or nut tree, then make some mounds. The bigger they are the better they work and the harder they become to mow around. I have made them with everything from a shovel to a bulldozer. The pits catch and store water while the mounds provide drainage for the root crown.
Taking pits and mounds a step further, we can create swales and berms to plant rows of trees on. These rows can be set on contour lines to maximize water catchment and prevent erosion.
Virtually all literature on chestnut cultivation speaks of the trees’ demands for acidic soil. However, I believe this depends on individual trees and species. I have on several occasions witnessed very healthy, mature chestnuts growing in alkaline soils. I believe that trees containing European and Japanese genetics are more likely to tolerate alkaline soil, but I have no scientific evidence to back this up.
Conventional wisdom is to plant trees on 40 foot centers. This is a big area for a small seedling to take up. Eventually the trees will be very large (in some old European orchards, only 4 trees fit per acre). There are several ways people have chosen to use the space that is not yet taken up by the young tree.
One method is to interplant chestnuts with shorter lived species such as peaches, raspberries, and asparagus. By the time the chestnuts are spreading their shade, these other plants will be on the decline. With the same ideology, some farmers use alley cropping to grow vegetables, grain, or hay in between the rows until the chestnuts get big.
My favorite method for spacing chestnuts is to breed them along the way. I plant rows of chestnuts with trees only a few feet apart. As the trees mature, I will thin out all but the best producing trees. This may sound expensive, but it is far cheaper than purchasing grafted trees, especially if you propagate your own seedlings.
Pests & Diseases:
There are a few pests that can cause damage to chestnuts. A single grower is unlikely to encounter all of these. Chestnuts have far fewer pests to worry about than most fruit trees.
Chestnut Weevils: The chestnut weevil is the most difficult and notorious to deal with, especially for the organic grower. There are two species, curculio sayi gyllenhal, and curculio caryatrepes boheman. Essentially they cause the same damage and have the same life cycle.
When burs are forming in late summer, the adult chestnut weevil will fly up and lay eggs into the nuts. The eggs won’t do anything until the nuts fall from the tree. At which point they’ll start chewing their way through the nut and eventually emerge anywhere from 3 days to 3 months after nut fall. They look like disgusting small white worms and ruin the nuts. After they exit the nut, the weevils burrow down in the soil and emerge the next year to fly up and lay eggs.
Two methods of organic control of chestnut weevil exists today. The first is sanitation. This means keeping a chestnut planting clean and free of fallen nuts. The life cycle of the weevil is broken if they can not emerge out of the nut into the ground. Every nut has to be harvested for this to work, and there can not be unmanaged trees nearby (within a mile). Livestock can help thoroughly harvest all the nuts.
If orchard sanitation is not an option because of wild trees nearby, then hot water treatment can be used. This involves prompt harvesting of the nuts. When the chestnuts first hit the ground, the eggs are very small and unnoticeable. If the nuts are put into a hot water bath the same day, then the eggs will be killed before they mature into the larvae. In order for the nuts to not be cooked or killed in the bath, the temperature can not exceed 140 degrees fahrenheit, and they should not be left in for more than 40 minutes. Some sources recommend 120 degrees for 20 minutes, but sometimes this proves inadequate, and some larvae will survive, thoroughly grossing out anyone who finds them wiggling around in their fridge.
Ambrosia beetles: These are a relatively new pest that tunnel into the trunks of young trees and form galleries where they cultivate pathogenic fungi. Untreated, ambrosia beetles will kill a young tree within a week or two. However, you can save trees that have been invaded. If you see small white sticks of frass perpendicular to the trunk, ambrosia beetles are in there. Immediately spray the trunk with pyrethrum. Ambrosia beetles only attack trees during a very short window, when the leaves are first emerging but not yet full size. Once leaves are full size, the trees are safe for the year. So, checking young trees every spring during this time can save them.
Asian Chestnut Gall Wasp: This wasp was accidentally introduced into the U.S. in 1974 on infested scion wood. The wasp lays eggs into the shoots of chestnut trees and galls are formed. The larvae feeding inside the galls severely damages the new shoots of trees. Asian chestnut gall wasp is considered a major pest where it is prevalent, primarily in the Southeast. It can severely limit tree growth, and therefore nut production.
Growers in areas without Asian chestnut gall wasp should avoid importing seedlings or cuttings from areas known to have it. This has been the primary way the wasp has spread.
Chestnut Blight: Cryphonectria parasitica has been totally devastating to American chestnuts and Ozark chinquapin, and very damaging to European chestnuts. Chestnut blight is a fungus spread by wind, insects, birds, and tragically nursery stock. It is native to Asia, where trees have evolved to live with chestnut blight. For trees that are susceptible to blight, the fungus feeds on the cambium layer and girdles the tree. Interestingly, chestnut blight can not kill the roots of a tree. There are too many competing fungi in the soil for chestnut blight to live. Some people have been able to keep American chestnut trees alive by applying mud packs to any blight cankers. This allows the tree to heal over the canker.
The more common and practical method for dealing with blight is to plant resistant trees. There are endless sources for resistant hybrids and Asian chestnuts. There is a strong movement to find and breed resistant American trees, this is covered in greater detail in my article “Epic Saga of the American Chestnut”.
If you live anywhere in the eastern U.S., there is blight in your area. Few people realize how common wild American chestnut sprouts are. Also, the fungus is able to remain dormant for decades, and the spores can travel hundreds of miles.
Ink Disease: Phytopthera cinamomii is just as terrible for chestnut trees as is the blight. Before the blight hit the U.S., ink disease wiped out millions of trees in the coastal regions of the South. Ink disease has not been a problem in the North. Unlike chestnut blight, ink disease kills the entire tree, roots and all.
Ink disease thrives where soils become saturated for part of the year. There is no treatment for trees that get ink disease. The best plan is to plant resistant trees in well drained sites if ink disease is in your area.
Deer and Rodents: It is essential to protect young trees from deer browse and girdling by rodents such as voles. Chestnut trees are just as appetizing to these critters as fruit trees are.
All these pests and diseases may sound overwhelming, but it is most likely that a grower will only have to deal with one or two. Compare this to a crop like apples, and chestnuts are relatively maintenance free.