Green Man Publishing

Chestnut

Castanea sativa

The sweet chestnut differs from most of the fruiting trees discussed here in that it is a big, beautiful forest tree. It is something you might think about planting if you have a lot of room and have planted everything else you want.

I really got into Chestnuts when I moved to my present land and found several trees already growing here. They were fairly small when I moved here but have grown rapidly and now provide a significant annual harvest.

Nutrients: The nuts are different from most nuts in that they are low in protein and fat, but very rich in complex carbohydrates. They also contain fiber, manganese, potassium, phosphorus, iron and vitamins B2, C and E

About Chestnut

Hours of winter chill: 400-750

Size – up to 80 feet x 50ft wide.

Zone: 5-9

Blooming period: Mid summer

Fruiting period: October – November

Life expectancy: 75-200 years

Bearing age: 3-6 years

Yield: 50 – 200lb

Days to harvest:

Spacing: Standard tree 50ft apart

Ease of growing: If you give them the right conditions few plants are as easy to grow as chestnuts. I don’t do anything at all except harvest the fallen nuts. They produce a crop of nuts regularly (in my garden they haven’t missed a year yet) and can be amazingly productive.

Climate

Chestnuts are hardy to about –20° F, but their preferred climate is Mediterranean hills (to 4000ft) with mild winters and hot summers. They are very drought tolerant and have essentially naturalized in gardens around here.

Soil

pH 5.5 – 8.0

These large forest trees prefer a deep, fertile, well-drained soil.

Site: The chestnut is significantly larger than most food bearing trees and will only work in a large site. It needs full sun for best production, but small trees are quite shade tolerant.

In poorly drained soils you may have to plant on a mound, to keep the collar of the tree from staying wet for long periods (too much water could cause it to rot).

Planting

In mild climates chestnuts can be planted at any time from late fall to early spring. In colder climates they are usually planted in spring. As with most other plants a small tree transplants better than a large tree and will do better in the long run.

How: Dig the planting hole 2‑3 times as wide as the root ball, to give the roots plenty of loose soil to grow into. You want the hole to be the same depth as the root ball (or roots if bare root), so it can be set into the ground at the same depth it was growing in the nursery. This is most easily measured by laying a stick across the hole to get the right height. The graft union should be 3-6” above the soil.

Start planting by throwing a couple of shovels of soil (possibly mixed with some organic matter if the soil is poor – to help it hold moisture) into the bottom of the hole. Make this into a slight mound and then spread the roots out evenly over it. You then put some soil in the hole to anchor the tree in place and firm it down. Then re-fill the hole with the rest of the soil (make sure the tree remains vertical). You may also want to add some rock phosphate to the soil as you go.

When you have finished planting the tree should be on a slight mound, so as the soil settles it becomes flat. If it starts out flat it may end up as a slight depression where water can collect (which can be a problem on poorly drained soils).

You then water the tree thoroughly, not only to supply water to the plant, but also to settle the soil and establish contact between roots and soil.

The final step is to spread out a mulch to conserve water, and keep down weed competition (keep this six inches away from the trunk).

It is also a very good idea to put a permanent label on the tree saying the variety and rootstock (and write it down in your garden journal).

Support: Newly planted trees were once routinely supplied with a stake to support them, but it is now thought that trees become stronger more rapidly if not staked. Staking is only usually necessary on very windy sites (especially for dwarf trees which grow on weak rootstocks).

Protection: If gophers live in your area you will have to plant your trees in gopher wire baskets (I make my own to whatever size I need). If other rodents are a problem (they may chew on the bark, stunting or even killing the tree) you may have to use various kinds of metal or plastic mouse guards. These should go several inches into the ground and should have gravel around them to deter digging.

Maintenance: Chestnuts don’t need any attention once established, though when they start fruiting you may want to rake up the spiny burrs after they have all fallen (they compost easily).

Fertilizing: These aren’t very hungry trees and don’t usually need additional fertilizer.

Watering: Mature trees are quite drought tolerant and have deep roots that can search out water. The trees in my garden produce well without any irrigation at all.

Of course newly planted trees will probably require some water in their couple of years, until they get established.

Pollination: Chestnuts are cross-pollinated by the wind, so you need more than one tree to produce fruit. The flowers appear in summer, long after any frost danger has passed.

Pruning: Chestnuts are terminal bearing, which means they produce fruit at the end of new growth. They can be grown without pruning, though you may need to remove some lower limbs to allow more light to get through to the ground (their foliage is very dense).

Propagation: Chestnuts are easily grown from fresh seed (they lose viability rapidly as they dry out) and self-sown (or squirrel sown) seedlings appear all over my garden. These grow very fast in the right conditions, but may take 10 years to start bearing much fruit. Improved cultivars can be grafted and usually bear at an earlier age. Cuttings.

Mulch: A mulch of compost is useful to keep the ground moist, and supply nutrients.

Problems

Some people dislike having fruiting chestnut trees in the garden because of their painfully spiny husks (my dog is reluctant to walk on them). If you want to use the area underneath the trees, it is a good idea to rake them up as they fall and compost them (they break down very quickly). These spiny husks serve an important function as they effectively prevent squirrels from eating the nuts before they are fully ripe.

Pests: So far they have been completely pest free in my garden, but in less favored areas they have their problems.

Chestnut weevil:

Chestnut Blight: Unfortunately it isn’t possible to grow European or American Chestnuts in the eastern part of the country because they are susceptible to Chestnut Blight. This introduced disease wiped out almost all of the American Chestnuts in its native range (this has been called the greatest ecological disaster in American history). Fortunately we can still plant the smaller Japanese and Chinese Chestnuts, as they are resistant.

Harvest; When the nut is ripe the spiny burr splits open and falls to the ground (which is good because they would otherwise be pretty inaccessible). The nuts often fall out on their own, but if they don’t just roll the husk under your foot to release the nuts. A ripe nut is chestnut brown (presumably this is where the name of the color comes from). The burrs are covered in needle-like spines and are pretty uncomfortable to handle. It’s a good idea to go out at least once a day and pick up the fallen nuts otherwise rodents will take them.

Storage: The fresh nuts deteriorate quickly and should be treated more like a vegetable than a nut. They can be stored in a perforated plastic bag, in the fridge, for up to a month. For longer term storage they can be dried.

Landscape uses: This is a big and beautiful shade tree. It is quite fast growing, but still takes at least 10 years before it starts to supply much shade.

Other uses: Chestnut wood is strong and rot resistant and has been called the most useful temperate hardwood. The trees produce little sapwood and so are rot resistant even at a young age. They have long been prized for use as fence posts.

Chestnut trees can be coppiced to provide poles for garden use (coppicing means cutting down the tree at ground level and allowing it to resprout and send up new poles). The new shoots grow very rapidly on their already established roots (my tallest shoots have grown 10 ft this summer) and can be cut every 3-10 years (depending upon the climate and the size poles needed). You can coppice any tree that gets too big for the garden and allow it to start all over again.

Food uses: Unlike most common nuts, chestnuts are high in carbohydrates rather than protein or fat and in the kitchen they are treated more like a cereal than a nut.

The nuts are commonly roasted, boiled or ground into flour for baking.

Varieties:

There are four important chestnut species and all have been extensively hybridized, unfortunately most improved varieties are hard to find. The only commonly available one is Colossal.

European Chestnut (Castanea sativa) Large nuts, heat tolerant. Susceptible to blight

Chinese Chestnut  (C. mollissima) Smallest tree but produces large nuts. Blight resistant.

American Chestnut (C. dentata) Biggest tree but small nuts. Susceptible to blight.

Japanese Chestnut (C. crenata) Large nuts but somewhat inferior.

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