July Tree of the Month-Kentucky Coffee Tree

The Kentucky coffee tree (Gymnocladus dioicus) is considered rare by conservation standards regarding its native distribution. Although rare in the wild, as a domesticated species, it’s becoming more popular in parks, public gardens, and as a street tree.

The large size, (up to 100′ high), and coarse texture put off most homeowners.  Once they spot the large seed pods and learn about the toxicity, that cinches things. However, it is a fascinating tree for plant geeks and tree lovers with its bi-pinnate leaves and interesting history.

The large bi-pinnate leaves, up to 3′ long, are made up of smaller 2-3″ blue-green leaflets attached to multiple pinnae…meaning the leaves are twice-divided (Whereas an ash or black walnut leaf is once divided with leaflets attached to only one pinnae.)

Coffee trees are dioecious, meaning they are separate male and female trees (Hence the specific epithet, dioicus). Only the female trees produce clusters of whitish flowers followed by large fruit pods and a nearby male is required in order for the females to produce fruit. The flowers in late spring are usually hidden by the foliage and aren’t considered showy but are fragrant.

The large seeds are toxic unless cooked. Native Americans and early settlers brewed them to make a caffeine-free substitute for coffee, leading to the common name. (According to North Carolina State Extension, both leaves and seeds are considered to have a low toxic rating.)

Because the seed pods are so large and can’t be dispersed by wind or small animals, they can usually only be dispersed by streams or rivers in the wild. Rumor has it that in prehistoric times, large, now-extinct mammals probably ate the pods, thus dispersing the seeds far away from the parent tree. This might explain why the tree is considered rare in the wild.

Full sun and moist, rich woodland soil is preferred, but the coffee tree tolerates dryer soils in parks and along streets.

Male cultivars are available for those who wish to avoid the large seed pods.

• ‘Espresso’: Vase-shaped with arching branches.
• ‘Prairie Titan’: Upright spreading shape with slightly blue-green foliage.
• ‘Stately Manor’: A narrower upright form that can still reach 50 feet wide at maturity.

What I love about this plant;

-It’s native!

-Large, interesting leaves.

-Unusual, beautiful seed pods that are ornamental.

-The history.

What’s not so great;

-The large mature size can be a con if you have a small space. Give it a LOT of room.

-The seed pods can be beautiful but messy, along with the large leaf pinnae.

-Seeds are toxic unless cooked.

–Coffee trees are one of the last trees to leaf out in the spring and one of the first to drop leaves in the fall, so they spend half the year bare. This attribute is not only the reason behind the genus name Gymno (naked) cladus (branch) but should be considered when used in designs.

Comments or questions? Email Garden-Lou at gardenloustl@gmail.com

Words and photos by Jo Batzer

© Jo Batzer, garden-lou.com-2024, All rights reserved.