Gymnocladus dioicus | Family: Fabaceae

Submission: Nimco Jama and Jack Daoust

Identification:

Leaves – Deciduous, alternate, pinnately compound; leaflets elliptical-ovate, entire, dull, dark blue-green

Twigs: Stout; buds small, downy, deeply sunken, surrounded by an incurved hairy ring of bark

Fruit/Cone – Stout, woody, dark reddish-brown legume, 4”-10” long; persistent

Bark – Thick, dark gray, scaly

Silvics – A medium-sized intolerant tree; uncommon species native to central US; dioecious 

Natural History:

Kentucky coffeetree (Gymnocladus dioicus), also known as the American coffee berry, is a medium-sized, dioecious tree that can reach upwards of 70 feet tall at maturity. The scientific name Gymnocladus is derived from the Greek words “gymnos” and “kladus” which mean “naked” and “branch” respectively and refer to the sinewy, twisting branches that remain on the tree after the fruit and leaves have fallen off.

The species has a relatively slow growth rate.  It is native to the Midwest, Appalachia, and parts of New York and Ontario, where it is most commonly found standing alone in prairies and open woods with optimal access to sunlight. While intolerant of shade this tree is highly adaptable to various soil types and acidities and thus can be planted in alkaline, rocky, or dry soils. Historically, the species was also planted in its native range of Appalachia on mines to help restabilize the soil and prevent further environmental damage.

Due to the Kentucky coffeetree’s outstanding tolerance for city conditions, the species has also been used as an ornamental outside of its native range throughout areas of the Northeast. The tree’s large upper canopy, which can reach 40-50 feet in diameter, encourages people to plant it in suburban areas, adding shade to sidewalks and walkways. Selective breeding has occurred for predominantly male individuals to reduce the litter created by individuals dropping their fruit in the spring.

As a member of the legume family (Fabaceae), the Kentucky coffeetree derives its name from its distinct pod-like fruits which ripen at the end of the summer. Despite their appearance, Kentucky coffeetree’s large pods and leaves are poisonous to eat and thus the tree is placed at a huge disadvantage as animals who would otherwise help it germinate tend to avoid it. Instead, Kentucky coffeetree relies heavily on running water to disperse its seeds that are protected inside its large, dark, and reddish-brown pods. Both male and female individuals bloom during the early spring months producing small white flowers arranged in pannicles at the end of each branch. 

The Kentucky coffeetree is thought to have first been introduced to Kentucky by indigenous peoples of the region who would use the tree’s pulp and leaves as a treatment for insanity and constipation. The first written conversations about the tree date back to 1784, when a United States general gave Kentucky coffeetree seeds to Thomas Jefferson as a gift, encouraging him to utilize the roasted seeds as a coffee substitute. While the seeds are poisonous if consumed raw they can be roasted to remove the alkaloid cytisine, thus making them safe for consumption. At present, there has only been one reported case of human poisoning by a Kentucky coffeetree. While the wood is rarely used as a source of lumber, the leaves and fruit continue to be used in products ranging from soap to insect poison.

References:

Johnstone, William C. The Kentucky Coffeetree – Filson Historical.Org, 1977. Online Resource.

Row, John M, Geyer, Wayne. “Kentucky Coffeetree.” USDA Plants Database, United States Department of Agriculture Natural Resources Conservation Service, 2023. Online Resource.

Seiler, John. “Virginia Tech Dendrology.” Kentucky Coffeetree Fact Sheet. Virginia Tech Dept. of Forest Resources and Environmental Conservation, 2017. Online Resource.

Shane, J. Dendrology Handbook, University of Vermont, 2008. Unpublished. Pg 85

University of Kentucky. Kentucky Coffeetree. Department of Horticulture, 2023. Online Resource.

University of Uconn. Gymnocladus dioicus: Kentucky Coffeetree. College of Agriculture, Health and Natural Resources, 2015. Online Resource.