Gymnocladus dioicus

The Kentucky coffeetree, Gymnocladus dioicus, is a tree in the subfamily Caesalpinioideae of the pea family Fabaceae, native to the Midwest and Upper South of North America. The seed may be roasted and used as a substitute for coffee beans; however, unroasted pods and seeds are toxic. The wood from the tree is used by cabinetmakers and carpenters. It is 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. The tree varies from 18 to 21 meters (60–70 feet) high with a spread of 12–15 meters (40–50 feet) and a trunk up to one meter (3 feet) 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 4 meters (13 feet) tall. It usually separates 3 to 4½ meters (10–15 feet) 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 15–21 m (50–70 ft). 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. The bark is ash-gray and scaly, flaking similarly to black cherry, but more so. The trees are dioecious, and the fruit is a hard-shelled bean in heavy, woody, thick-walled pods filled with sweet, thick, gooey pulp. Pod length ranges from 5 to 10 inches (130 to 250 mm); unfertilized female trees may bear miniature seedless pods. The beans contain the toxin cytisine. The Kentucky coffeetree is believed to be an example of evolutionary anachronism. The tough, leathery seed pods are too difficult for many animals to chew through (in addition to being poisonous) and they are too heavy for either wind or water dispersal. It is thus believed that the tree would have been browsed upon by now-extinct mammoths and mastodons 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. Gymnocladus is derived from the Ancient Greek κλάδος (kládos) 'branch' and γυμνός (gumnós) 'naked' and refers to the stout branchlets unclothed with small twigs. It is one of three species in the genus Gymnocladus, the other two being native to eastern Asia. These are Chinese coffeetree Gymnocladus chinensis in central China, and Burmese coffeetree Gymnocladus burmanicus in Burma.