The four main species of chestnuts are the American (Castanea dentata), the Chinese (C. mollissima), the European (C. sativa), and the Japanese (C. crenata). “Korean” chestnuts are Japanese or Chinese/Japanese hybrids but have characteristics that distinguish them from chestnuts native to Japan or China. Three minor species of chestnut are the American chinkapin (C. pumila and others), the Seguin (C. seguinii) and the Chinese chinkapin (C. henryi). The species called “chestnuts” characteristically bear 3 nuts inside spiny burs, while the species called “chinkapins” usually bear one nut per bur. Within all chestnut species there is tremendous genetic variation, especially in the Chinese, European, and Japanese species, which are somewhat domesticated. The variation within species may be greater than the variation between species. Nevertheless, there are some general characteristics of species that are distinguishing and noteworthy.
The American chestnut is (was) a tall, straight canopy dominant forest tree in eastern North America, valued as a timber tree as much as a nut producing tree. The nuts tend to be small, but easy-to-peel and exquisitely flavored. At the northern extent of its range, the trees are very cold hardy. On the downside, American chestnuts are very susceptible to chestnut blight and phytophthora root rot. These disease susceptibilities have essentially removed the tree’s ecological and economic importance, but enough of the species’ population remains that it can be utilized in breeding – either to create disease resistant American-type chestnuts or to incorporate American characteristics into hybrids.
The Chinese chestnut, native to China, is the most genetically diverse species and may be considered the progenitor species from which all other species were derived. It is generally a branchy, medium-sized tree, ultimately attaining about 2/3 the height of the American chestnut, but it does vary considerably in in its growth habit. Its nuts vary in size from small to large and are generally easy peeling and quite tasty with bright yellow kernels. The species has broad climatic adaptation and disease resistance. It is well-adapted to growing conditions and disease pressures in eastern North America and is well-liked by consumers.
The Japanese chestnut, native to Japan and the Korean peninsula, is a medium to large-sized tree with some individuals growing faster and taller than Chinese chestnuts, but still shorter than American chestnuts. Its nuts range to a very large size, but generally are difficult-to-peel and have a bland flavor, with some individuals tasting bitter or astringent. The kernels are generally white or cream-colored. The species tends to be vigorous, precocious and high yielding with disease resistance comparable to Chinese chestnuts. It has broad climatic adaptation with some individuals exhibiting more cold hardiness and cool growing season tolerance than Chinese chestnuts.
The European chestnut, native to southern Europe and Asia Minor, is a large-sized tree with a reputation for longevity. It is cultivated for both timber and nuts. The nuts are medium to large size with whitish kernels, and some are difficult to peel. Flavor is variable with some cultivars quite tasty, better cooked than raw. European chestnuts are susceptible to chestnut blight and phytophthora, and most are not very cold hardy. They seem to thrive in Mediterranean-type climates, and consequently, do well in the west coast states of the USA and in southwestern British Columbia. In Europe and in western USA, there are now many cultivars that are European-Japanese hybrids. These hybrids tend to have larger nut size, higher productivity, and higher disease resistance, but with diminished flavor and peeling characteristics.
The North American chinkapins are a genetically diverse group, which some taxonomists have divided into 2 or more species. The two commonly recognized groups are the Allegheny chinkapin native to southeastern USA and the Ozark chinkapin native to the Ozark plateau but with populations scattered across the southeastern states. Chinkapins are shrubs to medium sized trees and are characterized by bearing very small nuts, one per bur. The nuts are tasty, but their tiny size render them difficult to harvest and eat. They are a premier wildlife food, especially for birds like blue jays and turkeys. They are susceptible to chestnut blight and phytophthora.
The Chinese chinkapin is native to southern China and is a large tree characterized by bearing one nut per bur. It has not been widely cultivated outside of China. It is not very cold hardy.
The Seguin chestnut, native to the southern part of the chestnut range in China, is a medium-sized tree. It bears small nuts, 3 per bur. Its unusual characteristic is that some individuals are ever-flowering; i.e., they continuously flower during the summer thus bearing nuts that ripen over a long period of time in the fall. It is not grown commercially and is little known.