The Kentucky coffeetree (Gymnocladus dioicus), also known as American coffee berry, Kentucky mahogany, nicker tree, and stump tree, is a tree in the subfamily Caesalpinioideae of the legume family Fabaceae, native to the Midwest, Upper South, Appalachia, and small pockets of New York in the United States and Ontario in Canada. The seed may be roasted and used as a substitute for coffee beans; however, unroasted pods and seeds are toxic.<!-- see text for more detail --> The wood from the tree is used by cabinetmakers and carpenters. It is also planted as a street tree.

From 1976 to 1994, the Kentucky coffeetree was the state tree of Kentucky, after which the tulip poplar was returned to that designation.

Description

The tree varies from high with a spread of and a trunk up to in diameter. The tree grows at a medium rate with height increases of anywhere from 12" to 24" per year. A 10-year-old sapling will stand about tall. It usually separates from the ground into three or four divisions which spread slightly and form a narrow pyramidal head; or when crowded by other trees, sending up one tall central branchless shaft to the height of . Branches are stout, pithy, and blunt; roots are fibrous.

The Kentucky coffeetree is a moderately fast-growing tree, and male trees are often grown in parks and along city streets for ornamental purposes. The tree is typically fairly short-lived, healthy trees living from 100 to 150 years. The Kentucky coffeetree sheds its leaves early during the fall and appears bare for up to 6 months. The naked appearance of the tree is reflected through the Kentucky coffeetree's Greek genus name, which means "naked branch". Like the Sumac, branches are absent of fine spray; smaller branches are thick and lumpish. Because of the absence of smaller branches and its later leafing, the French in Canada named it Chicot, "stubby". The expanding leaves are conspicuous because of the varied colors of the leaflets; the youngest are bright pink, while those which are older vary from green to bronze.

  • Bark: Tan or dark gray, deeply fissured, surface scaly, often with prominent narrow ridges. Branchlets at first coated with short reddish down.
  • Wood: Light brown; heavy, strong, coarse-grained; durable in contact with the ground, takes a fine polish. Specific gravity, 0.6934; weight of cubic foot, .
  • Winter buds: Minute, depressed in downy cavities of the stem, two in the axil of each leaf, the smaller sterile. Bud scales two, ovate, coated with brown tomentum and growing with the shoot, become orange green, hairy and about one inch long, before they fall.
  • Leaves: Alternate, bipinnately compound, ten to fourteen pinnate, lowest pinnae reduced to leaflets, the other seven to thirteen foliate. One to three feet long, eighteen to twenty-four inches broad, by the greater development of the upper pairs of pinnae. Leaf stalks and stalks of pinnae, are terete, enlarged at base, smooth when mature, pale green, often purple on the upper side. Leaflets ovate, two to two and one-half inches long, wedge-shaped or irregularly rounded at base, with wavy margin, acute apex. They come out of the bud bright pink, but soon become bronze green, smooth and shining above. When full grown are dark yellow green above, pale green beneath. In autumn turn a bright clear yellow. Stipules leaf-like, lanceolate, serrate, deciduous.
  • Winter twigs are very stout and dark reddish brown to green brown in color; the pith is very thick and salmon pink to brown in color. The terminal bud is absent, and the lateral buds are small, bronze in color, and appear to be partially sunken beneath the bark of the twig. The leaf scars are very large, heart shaped with 3 to 5 conspicuous bundle scars. The flowers are dioecious (male and female flowers on separate plants). The female flowers are 8 to 12 inches long, greenish white in color, appear in early summer, and are quite fragrant. The male flowers are about half the size of the female flowers.
  • Flowers: June. Dioecious by abortion, terminal, greenish white. Staminate flowers in a short raceme-like corymb three to four inches (75–100&nbsp;mm) long, pistillate flowers in a raceme ten to twelve inches (250–300&nbsp;mm) long.
  • Calyx: Tubular, hairy, ten-ribbed, five-lobed; lobes valvate in bud, acute, nearly equal.
  • Corolla: Petals five, oblong, hairy, spreading or reflexed, imbricate in bud.
  • Stamens: Ten, five long and five short, free, included; filaments thread-like; anthers orange colored, ; in the pistillate flower small and sterile.
  • Pistil: Ovary superior, sessile, hairy, contracted into a short style, with two stigmatic lobes; ovules in two rows.
  • Fruit: Legume, six to ten inches (150–250&nbsp;mm) long, one and one-half to two inches wide, somewhat curved, with thickened margins, dark reddish brown with slight glaucous bloom, crowned with remnant of the styles. Stalks an inch or two long. Seeds six to nine, surrounded by a thick layer of dark, sweet pulp.
  • Soil: Prefers rich, moist soils in floodplains, terraces, ravines, coves, and lower slopes.

This tree usually occurs as widely dispersed individuals or small colonial groups with interconnected root systems. This tree is found in floodplains and river valleys but is also sometimes seen on rocky hillsides and limestone woods. In the northeastern part of its range, seemingly natural groves of this tree are actually associated with known prehistoric village sites. In some parts of its range, this tree may be used as an indicator of the presence of limestone or of calcareous soils.

The Kentucky coffeetree is considered an example of an evolutionary anachronism. The tough, leathery seed pods are too difficult for many extant animals to chew through (in addition to being poisonous) and they are too heavy for either wind or water dispersal. It has been hypothesized that the tree would have been browsed upon by now-extinct mammalian megafauna, which ate the pods and nicked the seeds with their large teeth, aiding in germination. This behavior is seen among African elephants eating Fabaceae relatives in Africa. Because of this, its prehistoric range may have been much larger than it has been in historical times. Today, in the wild, it only grows well in wetlands, and it is thought that only in such wet conditions can the seed pods rot away to allow germination in the absence of large herbivores. It is protected in some but not all parts of the Canadian province of Ontario.

Uses

thumb|upright|Kentucky coffeetree (upright trunk) at Minnesota Landscape Arboretum

Cultivation

Gymnocladus dioicus is considered well-suited to urban environments, as it is tolerant of poor soils, has extreme drought tolerance, and is not vulnerable to serious insect infestations or disease problems. It is cultivated by specialty tree plant nurseries as an ornamental tree for planting in gardens and parks. The peculiarly late-emerging and early-dropping leaves, coupled with the fact that the large leaves mean few twigs in the winter profile, make it a tree that is ideal for urban shading where winter sunlight is to be maximized (such as in proximity to solar hot-air systems).

It is often planted because of its unique appearance and interesting character.

Food

The beans of the tree were eaten, after roasting, in the Meskwaki (Fox), Ho-Chunk (Winnebago) and Pawnee Native American cultures.

The Meskwaki also drank the roasted ground seeds in a hot beverage similar to coffee. especially in times of poverty, similar to chicory. The European colonialists, however, considered it inferior to real coffee: