Gymnocladus dioicus (Kentucky Coffee Tree)

Plant Info
Also known as:
Genus:Gymnocladus
Family:Fabaceae (Pea)
Life cycle:perennial woody
Origin:native
Status:
  • State Special Concern
Habitat:sun; moist; rich woods, floodplains, urban landscapes
Bloom season:May - June
Plant height:50 to 70 feet
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 5-petals Cluster type: raceme

[photo of male flowers] Loose clusters of stalked flowers at branch tips, with male and female flowers on separate trees, though some trees can have perfect flowers (both male and female parts). Male clusters tend to be shorter with fewer flowers, females up to 7½ inches long with 25 to 50 flowers. Flowers are greenish white, ½ to 5/8 inch across with 5 narrow, oblong petals alternating with 5 sepals that are narrower than and about as long as the petals. In the center is a column about half as long as the petals, containing 10 stamens and/or a single style depending on the sex of the flower.

[photo of calyx tube] The calyx tube (hypanthium) at the base of a flower is about ½ inch long, green to dark purplish. Surfaces of petals, sepals and the calyx tube are densely covered in short hairs. Flower stalks are up to 1 inch long, hairless, stiff and erect.

Leaves and bark: Leaf attachment: alternate Leaf type: compound

[scan of compound leaf] Leaves are alternate, twice compound, up to 3 feet long and 2 feet wide with 5 to 9 pairs of pinnae (branches), each with 3 to 7 pairs of leaflets. Often at the base of the compound leaf are 1 or 2 pair of opposite leaflets that are larger than the pinnae leaflets. Leaflets are mostly egg-shaped, tapering to a pointed tip and rounded at the base, 1½ to 3½ inches long, ¾ to 1½ inches wide, toothless, the edges smooth or with a fine fringe of hairs. Upper surfaces are smooth or with scattered hairs, the lower surface hairy along the main veins. Leaflet stalks are about 1/8 inch long and smooth to hairy. Fall color is a deep gold.

[photo of twig] Young twigs are brown, hairless with light brown to orange lenticels (pores), stout and knobby, the main leaf stalks of the previous season often persisting in winter, giving branches a finer twiggy appearance.

[photo of trunk] Branches become dull gray or gray-brown, the bark coarsely textured with shallow fissures and scaly plates. The trunk can reach 24 inches in diameter at breast height (dbh).

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is a large, leathery, flattened pod up to 6 inches long and 1½ inches wide, green in summer drying to purplish brown.

[photo of seeds in pulp] Inside are dark brown seeds surrounded by a sticky pulp. Seeds are smooth and very hard, oval but somewhat flattened, 3/8 to ½ inch long and about 5/8 inch diameter.

Notes:

Preferring rich, moist woodlands, Kentucky Coffee Tree is noted as uncommon throughout its North American range. A factor in this is while it produces abundant seeds, their hard, impervious seed coat causes them to be highly resistant to natural germination. It has been suggested that the species evolved requiring ingestion by large herbivores now long extinct. It does, however, reproduce by root suckers and where found today, it often exists as clonal colonies of younger trees, all descended vegetatively from an ancient parental origin. It was listed as a MN Special Concern species in 2013 due to its small natural populations and limited range in the state, combined with concerns over reproduction and viability of the gene pool. Though Kentucky Coffee Tree is known to contain poisonous alkaloids, they are destroyed by the cooking process and early native Americans used the seed for a variety of culinary and medicinal uses as well as recreational (dice) purposes, and likely had some impact on its present distribution. Early settlers did indeed use the seeds for a coffee-like substitute beverage but it was not very popular compared to the real thing. It is propagated and planted in both urban and rural landscapes today, however selections have been made of male trees that won't produce the somewhat messy fruit, and its coarse, stiff branching causes it to be easily damaged by handling in the nursery trade.

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More photos

Photos by K. Chayka taken at Battle Creek Regional Park, Ramsey County. Photos courtesy Peter M. Dziuk taken at numerous urban locations in the Twin Cities Metro area.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Dawn - Wells mn
on: 2016-06-06 19:28:14

I have one in my back yard. Must be a male because it does not produce fruit. Great shade tree, but, very messy! Sheds its flowers and then the sticklike branches in late fall.

Posted by: Ellen S. - Hennepin County - Minneapolis
on: 2016-10-29 15:46:25

The Bakken Museum has a female tree.

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