(News article for November 12, 2022)

As we approach the season of “chestnuts roasting on an open fire,” I thought I’d write about some trees that are not discussed all that often here in Louisiana.

If you’ve traveled outside of the US and wondered why you were asked if you were carrying any plants or plant parts when you returned, the American chestnut (Castanea dentata) is part of the related history. The story of chestnut blight is one of the best-known cautionary tales about potential hazards of bringing plant materials into the country without sufficient precautions.

Symptoms of chestnut blight were identified in New York in the early 1900s, and the disease was widespread in the American chestnut’s native range by the mid-1920s. It is believed that the fungus that causes chestnut blight (Cryphonectria parasitica) arrived in the United States on Japanese chestnut (C. crenata) trees that were imported in the late 1800s or early 1900s.

Even before the spread of chestnut blight, American chestnut was not a major part of Louisiana’s tree canopy. Its range was largely associated with the Appalachian Mountains, though its presence has been documented in Morehouse and Webster Parishes in northern Louisiana and quite a few counties in Mississippi.

Prior to the introduction of chestnut blight, some American chestnut trees reached heights of more than 100 feet. American chestnuts have not been eliminated, because chestnut blight does not kill tree roots. Shoots grow from the base after tops die but do not typically live long enough to attain a size comparable to the tree’s historical stature.

Chinese chestnut (C. mollissima) trees are more resistant to chestnut blight than American chestnuts are. The two species have been crossed in efforts to breed trees that predominantly have characteristics of American chestnuts but are resistant to the disease.

Chinese chestnut trees can grow to roughly 40 feet tall and 50 feet wide. Planting two or more varieties is advised for cross-pollination. Here in the Florida Parishes, we’re near the southern end of the Chinese chestnut’s range.

Parts of southeastern and western Louisiana are within the native range of Allegheny chinquapin (C. pumila), a close relative of chestnut that also produces an edible nut. The chinquapin can grow to 50 feet tall, but it is susceptible to chestnut blight, and the top is likely to be killed before it reaches this size. Its appearance is often shrub-like. Both Chinese chestnuts and chinquapins should be planted on well-drained, sunny sites.

There are simple ways to differentiate among American chestnut, Chinese chestnut, and Allegheny chinquapin trees. The spiny burs on American and Chinese chestnut trees typically contain two to three nuts, while those of the Allegheny chinquapin contain just one. At the same time, the undersides of chinquapin and Chinese chestnut leaves are typically hairy, while undersides of American chestnut leaves are smooth.

Besides these three closely related species, there are others that look like chestnuts in one way or another.

Chestnuts and chinquapins, along with oaks, are in the beech family (Fagaceae). American beech (Fagus grandifolia) trees bear nuts within burs also, but burs are generally smaller than those of chestnuts and chinquapins. Also, beech bark is noticeably smooth and buds are long and cigar-shaped.

Sawtooth oaks (Quercus acutissima) are not native here but are sometimes planted for wildlife mast or ornamental purposes. Both the bristle-tipped teeth of leaves and the recurved scales on the “caps” (cupules) of acorns give the sawtooth oak a chestnut-like appearance. As with other acorns, though, part of the nut itself is exposed.

The swamp chestnut or cow oak (Q. michauxii) is commonly seen in parts of the Florida Parishes. While its name suggests a similar appearance to chestnut, the teeth along leaf margins are more rounded, and the acorns lack characteristics that would give a chestnut-like appearance.

The American Chestnut Foundation provides a handy table with additional information about distinguishing among chestnuts and relatives.

Let me know if you have questions.

Contact Mary Helen Ferguson.

Chinese chestnut burs. The spiny burs on American and Chinese chestnut trees typically contain two to three nuts. Nuts have already been released from the bur on the right. (Photo by M.H. Ferguson)

Chinese chestnut leaf. The undersides of chinquapin and Chinese chestnut leaves are typically hairy. (Photo by M.H. Ferguson)

Allegheny chinquapin leaves and burs. Burs of Allegheny chinquapin contain just one nut. (Photo: Chris Evans, University of Illinois, Bugwood.org)

The recurved scales on sawtooth oak acorn cupules are reminiscent of chestnuts, but as with other acorns, part of the nut itself is exposed. (Photo: Chuck Bargeron, University of Georgia, Bugwood.org)