American Chestnut

At a glance

• Botanical name: Castanea dentata
• Hardiness: USDA zones 4 to 8
• Mature size: 60 to 80 ft tall, 30 to 55 ft spread
• Spacing: 40 ft between trees
• Sun: full sun. Food forest layer: canopy
• Soil: well drained, acidic
• Pollination: needs a partner. Plant at least two
• First nuts: about 3 to 5 years
• Bloom: early summer. Harvest: late summer into fall
• Chill hours: 500 to 1000
• Growth rate: fast. Water: moderate
• Wildlife: the nuts feed nearly everything, deer, bear, squirrel and turkey included

Site and soil

Chestnuts are fussy about exactly one thing, and that thing is drainage. They grow best in deep, well drained soils without restrictive layers that limit root growth, and they cannot tolerate saturated root zones, which makes bottomland unsuitable (University of Missouri Extension). Acidic soil suits them. If a soil test puts you below the range, Missouri Extension recommends liming to a pH of 5.5 to 6.5 at establishment.

Give it full sun and give it room. A tree that finishes 60 to 80 feet tall with a 30 to 55 foot spread is a canopy tree, so the 40 foot spacing is not generosity, it is the plan. Crowd it and you will be cutting one of them down in fifteen years.

One more siting note that catches people out: chestnuts are highly frost sensitive in spring, so good air drainage matters. Plant toward the top of a slope and orient your planting so air moves through, rather than tucking the tree into a hollow where cold air settles (University of Missouri Extension). If you are at the cold edge of zone 4, take that seriously and pick a sheltered upslope site.

Planting

Plant in spring before budbreak (University of Missouri Extension). Dig the hole as deep as the root ball and wider than it, set the tree at the same depth it sat in the pot, and backfill with the soil you dug out. Never add fertilizer to the planting hole, because fertilizers are caustic and can burn and kill the roots of a young tree (NC State Extension). Water it in well.

Then mulch. Three to four inches of organic mulch from just outside the trunk to the dripline, shaped like a doughnut rather than a volcano, and keep the mulch back about 12 inches from the trunk so voles have to cross open ground to get to the bark (NC State Extension).

Plant two. Chestnuts require pollination from another tree, so put in at least two (NC State Extension), and keep partners within 200 feet of each other so the pollen actually gets where it needs to go (University of Missouri Extension).

First year care

The first season is water and competition, nothing clever. Clear grass and weeds out to the dripline and keep them out, because they compete directly for the soil moisture and nutrients a young tree needs (NC State Extension). Water deeply when it is dry rather than sprinkling every day, and hold the drainage rule in mind the whole time: chestnuts want steady moisture and will not forgive standing water at the roots (University of Missouri Extension). Our record lists this one as a moderate water tree once it is established.

Protect the trunk. A guard around the base keeps rodents off the bark (NC State Extension), and in deer country a cage or a tube costs a lot less than replacing the tree in year three.

Pruning

Young chestnuts ask for very little. In the dormant season take out anything broken, crossing or rubbing, and otherwise let the tree build leaf area, since leaves are what pay for root growth.

As it gains height, remove low or poorly placed branches a few at a time each year until the canopy clears whatever you mow or drive underneath. Orchard guidance from Missouri Extension stops that structural pruning once the trees are about 15 years old. After that you are only taking out damage.

Harvest

First nuts in about three to five years, which lines up with extension guidance of three to five years to harvest for chestnuts (NC State Extension). Male catkins bloom yellowish white in June into July, and the nuts follow from late summer into fall.

The burs are two to two and a half inches across and genuinely prickly. They open around first frost and drop two to three sweet, edible nuts each in September and October (NC State Extension). Gather daily while they are falling, the way orchards do (University of Missouri Extension), because nuts left on the ground get found by everything else first. Fresh chestnuts are not shelf stable the way a walnut is. Unpeeled, in an airtight container, they keep about a month in the refrigerator and a year or more in the freezer (NC State Extension).

Living with chestnut blight

Plant this tree with clear eyes. American chestnut is extremely susceptible to Cryphonectria parasitica, the blight that reduced it from a dominant forest tree to nearly extinct in its natural habitat (NC State Extension). The fungus enters wounds in the bark and forms swollen or sunken cankers. Every part of the tree above a canker eventually dies. The roots are not killed and send up sprouts, but those sprouts seldom live long enough to produce nuts (Penn State Extension).

So, practically: look over the trunk and main limbs once a season for sunken or swollen cankers, keep the bark unwounded by mowers and string trimmers, and do not make an American chestnut the only nut tree you are counting on for a harvest. Breeding programs are working toward a blight resistant tree that is still 94 percent American chestnut (Penn State Extension), and that work only exists because people kept putting the species in the ground. That is the side of the ledger we are on, and it is the reason we grow this tree.

Where these numbers come from

• NC State Extension Plant Toolbox: Castanea dentata
• NC State Extension Gardener Handbook, chapter 15: Tree Fruit and Nuts
• University of Missouri Extension, publication G739: chestnut orchard establishment and culture
• Penn State Extension, From the Woods: American Chestnut