December Plant of the Month: The Chestnut Tree

This month we’re talking about the chestnut tree. Also check out my previous Plant of the Month for November, The American Persimmon. December is the perfect month to talk about chestnuts (Castanea spp). The old-fashioned tradition of roasting chestnuts for the holidays conjures a cozy image, but most people alive today likely have never experienced it. The sad reason for this is chestnut blight, which killed nearly all the mature chestnut trees in North America and Europe.

In the Beech family (Fagaceae) and of the genus Castanea, chestnut is one of the most useful trees there is. It’s valuable not only as a food and lumber source but also for its ecologic value. Chestnuts can be giants, with some old-growth American chestnuts reaching one hundred feet tall and ten feet in diameter.

What is Chestnut Blight?

If you’ve read the book The Overstory by Richard Powers, you’ll remember its tear-jerking account of American Chestnut Blight. Around the turn of the twentieth century, a fungal pathogen (Cryphonectria parasitica) was introduced to North America from China. Within forty years, the fungus killed nearly all the American chestnut trees. More precisely, the aboveground portions of the trees were killed. Chestnut blight, being a pathogen infecting the bark, spares the root system, but fresh growth cannot reach maturity before again succumbing to the pathogen.

Chestnut blight was, according to Chestnut Hill Outdoors,” easily the greatest ecological disaster in American history.” Prior to the blight, chestnuts were a dominant species in the forest ecosystem of Eastern North America. Ecologists estimate that before the 1900s one in four trees in the Appalachian mountains were chestnuts.

Chestnut blight also affects European chestnuts (Castanea sativa) and spread across Europe during the early and mid-1900s, also decimating the native European chestnut populations. However, some European varieties have some resistance to chestnut blight. Asian chestnuts seem to have even more resistance, particularly the Chinese chestnut (Castanea mollissima).

Chestnut breeding programs aim to develop blight-resistant varieties and reestablish chestnut forests. One of these is the American Chestnut Foundation. Find more information in their 2023 documentary, American Chestnut: The Optimist of the Forest.

Chestnut Species

There are four prominent chestnut species: American Chestnut, European Chestnut, Chinese chestnut, and Japanese chestnut. In this article, I also mention the chinquapin chestnut, a smaller chestnut species with the potential for growing in smaller areas, or even as a dwarfing rootstock.

Common Name	Botanical Name	Tree Size	Nut Size	Blight Resistance
American Chestnut	Castanea dentata	100′ tall X 10′ trunk	1/2″-1″	Low to none
European Chestnut	Castanea sativa	95′ tall X 7′ trunk	1/2″-1″	Moderate
Chinese Chestnut	Castanea mollissima	40′ – 60′ tall	3/4″-2″	High (varies with variety)
Japanese Chestnut	Castanea crenata	35′ tall	1″-2″	High (varies with variety)
Allegheny Chinquapin	Castanea pumila	15′ tall	1/2″	None to moderate

Chestnut Tree Uses and Ecosystem Services

Chestnuts produce burred fruits with edible nuts, which typically fall to the ground when ripe. The nuts provide a nutrient-dense, high-carbohydrate food source, for both wildlife and humans.

Chestnut wood is a straight-grained, lightweight, rot-resistant hardwood. It provides quality lumber for landscape uses and construction. Its traditional uses were for utility poles, railroad ties, and house foundations, among others.

In its natural habitat, chestnut is a keystone species, meaning that it helps hold the ecosystem together. Historically, Autumn would see a carpet of chestnuts on the forest floor, providing forage for wildlife, and soil-building organic matter. The chestnut trees themselves provide shelter and habitat for other species. After losing these giant trees, the ecosystems changed drastically, with a steep reduction of biodiversity and resilience.

Growing Dwarf Chestnuts

The idea of growing chestnut trees in an urban food forest is appealing because of the tree’s immense ecosystem value and its quality food source. However, many chestnut trees are fast-growing giants that can reach ninety feet or more. Even Chinese chestnut trees can reach sixty feet. This is not appropriate for many backyard gardens.

Allegheny Chinquapin, also spelled chinkapin (Castanea pumila) grows much smaller than other Castanea species, up to about 15 feet tall in the wilds. Like their larger cousins, chinquapins provide an excellent source of food for wildlife and humans, with a sweet-tasting nut. They contain only one nut per bur, as opposed to three per bur in other notable species.

However, this species has undesirable qualities as well. Chinquapin nuts are smaller and more difficult to harvest than other chestnuts, making them a less practical human food source. This limits its potential as a commercial crop.

As far as I’m aware, not much work has been done on developing dwarf chestnut trees that produce high-quality nuts. However, there is potential to graft Chinese or blight-resistant American chestnuts onto chinkapin chestnut or oak rootstock to achieve a smaller tree.

Chestnut Cautions

The horse Chestnut, or buckeye, can be confused with true chestnut. Horse chestnuts are not closely related to true chestnuts and are in the genus Aesculus. Trees in this genus are often planted as ornamentals. They produce toxic, inedible nuts that resemble true chestnuts.

Less easily confused is the water chestnut, which is not a nut at all but an edible tuber of an aquatic herbaceous plant in the sedge family (Cyperaceae).

Something to consider before planting a chestnut tree is that some regions in the world (including parts of the Western United States) remain chestnut blight-free. When establishing chestnut trees in new areas, we must take special care not to introduce the pathogen.

Resources

NC State Extension – Chestnut Species

The American Chestnut Foundation

USDA – What it Takes to Bring Back the Near Mythical Chestnut Trees