Kentucky coffeetree
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 A Kentucky coffeetree in the winter
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| Gymnocladus dioicus (L.) K. Koch |
The Kentucky Coffeetree, Gymnocladus dioicus, is a tree in the subfamily Caesalpinioideae of the pea family Fabaceae, native to the midwest of North America. The range is limited, occurring from the far south of Ontario, Canada and in the United States from Kentucky (where it was first encountered by Europeans) and western Pennsylvania in the east, to Kansas,eastern Nebraska, and southeastern South Dakota in the west, and to northern Louisiana in the south. It was formerly the state tree of Kentucky.
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.
The Kentucky Coffeetree has immense bipinnate leaves, 60-90 cm in length, and about 2/3 as broad. The leaves emerge later in the spring than those of most other deciduous trees, and fall earlier in the autumn. This peculiar characteristic, 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). This tree is bothered little by heat, cold, drought, insects, disease, road salt, ice, and alkaline soil.
It forms large clonal colonies, reproducing by shoots sprouting from roots. The bark is ash-gray and scaly, flaking similarly to black cherry, but more so. The flowers are dioecious, and the fruit is a hard-shelled bean in heavy, woody, thick-walled pods filled with sweet, thick, gooey pulp. The shape of the pods varies somewhat: pod length ranges from ca. 12.7cm to 25.4cm; unfertilized female trees may bear miniature seedless pods. The beans contain the toxin cytisine.
Kentucky Coffeetree is easy to grow from seed. Filing the seedcoat by hand with a small file, and then soaking the seeds in water for 24 hours will ensure rapid germination. Propagation is also easy from dormant root cuttings.
The common name "coffeetree" derives from the use of the roasted seeds as a substitute for coffee in times of poverty. They are a very inferior substitute for real coffee, and caution should be used in trying them as they are poisonous in large quantities.
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 Myanmar.
The name is sometimes hyphenated as 'coffee-tree'; the form 'coffeetree' used here is as used officially by the United States Forest Service.
[edit] References
- Sternberg, Guy, (2004) Native Trees for North American Landscapes. Timber Press, Inc.
- University of Fort Smith Tree Guide Pod dimensions.
- Personal conversation with The Morton Arboretum regarding the occasional appearance of miniature seedless pods on female Kentucky Coffeetrees.
