Kentucky Coffeetree

Kentucky Coffeetree

Gymnocladus dioicus (L.) K. Koc

Description

Kentucky coffeetree is a member of the legume family (Fabaceae) and has numerous additional common names including American coffee bean, American mahogany, niker tree, and chicot tree.  ¹  Kentucky coffeetree is a deciduous tree that grows to 100 feet. ¹  Its dark, gray-grown bark is thick and forms plates that curl along the edges. ¹  It has alternate, bipinnately compound leaves that are almost a yard in length. ¹ There are up to 40 leaflets 7, each two to three inches long with a smooth margin. ¹  Flowering is “polygamo-dioecious”, ¹  meaning that some plants have bisexual flowers and male flowers while others have bisexual and female flowers on the same plant.   Other plants are strictly male or female. ² The flowers are greenish white and are wind-pollinated.  Female flowers are in foot-long terminal clusters. ²  Mature fruit are brown in color and up to 12 inches long and 2 inches wide. ¹  The fruit contain 4 to 8 very hard, black seeds that are 3/4-inch in diameter.

Gymnocladus dioicus - Kentucky Coffeetree

Outer bark of Kentucky coffeetree.  BioLib, T. Horova 8

Gymnocladus dioicus - Kentucky Coffeetree

Leaf of Kentucky coffeetree.  BioLib, M. Kesl8

Gymnocladus dioicus - Kentucky Coffeetree

Flowers of Kentucky coffeetree.  BioLib, M. Kesl 8

dark kentucky coffeetree pods, one broken open to show dark seeds inside

Fruit and seeds of Kentucky coffeetree.  Iowa State University, P. Wyra 7

Distribution

The natural distribution of Kentucky coffeetree is from New York to Minnesota, south to Kentucky and Tennessee.  It is nowhere abundant. ¹  In Maryland it is listed as S1 (highly state rare) with Garrett County as the only native location. 6  It is naturalized along the Potomac River drainage and in Baltimore and Kent counties. 6

Distribution of Kentucky coffeetree. 5

Wildlife Importance

Because all parts of the tree are toxic, there is limited wildlife importance. ¹

Economic Importance

The seeds and pods were used as a coffee substitute if they were properly roasted to degrade the toxins. ¹ They do not contain caffeine. ²  The hard wood takes on a deep shine and is dark orange or reddish brown ³ leading to its common name of American mahogany.  It is used for furniture, cabinets, interior finish and fence posts. ¹

Threats

There are no serious threats or diseases to the plants. ²

Interesting Facts

  • While a member of the legume family, Kentucky coffeetree is not associated with nitrogen fixation. ¹
  • The fruit and seeds are poisonous to humans causing stomach pain, nausea, vomiting and coma. ² It contains a toxic alkaloid, cystisine. ¹
  • The national champion Kentucky coffeetree is in Montgomery County, Maryland.  It measures 109 feet tall and 63 inches in diameter. 4

References

  1. USDA-NRCS Plant Guide:  Kentucky coffeetree
  2. North Carolina Extension:  Gymnocladus dioicus 
  3. The Wood Database:  Kentucky coffeetree
  4. Maryland Big Trees
  5. Gardens Rant:  Pour Me Another Kentucky Coffeetree
  6. Maryland Biodiversity Project:  Kentucky coffeetree
  7. Iowa State University–Extension and Outreach:  Kentucky coffeetree
  8. BioLib:  Gymnocladus dioicus

Contributed by J. Hull

Towson University Glen Arboretum

Towson University

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