- Created: Monday, 01 March 2021 14:41
Kentucky Coffeetree (Gymnocladus dioicus)
The Kentucky Coffeetree is an uncommon species in the urban setting but has gained attention among educational institutions. Tree expert Michael Dirr writes of the coffeetree in his Encyclopedia of Trees and Shrubs, on display in the Heiser lounge, "to know her is to love her. Among my top Noble Trees. A wonderful native species that tolerates the worst stresses nature and humanity can impose." It leafs out late in the spring and sheds its leaves early in the fall. This makes it a wonderful tall shade and ornamental tree during the heat of the summer. [Direct winter sunlight can reduce heating demands.] The naked winter branches give rise to its Greek genus name Gymnocladus which means naked branch. The naked branches make it easy to see perching birds and landscape beyond.
Coffetrees are either male or female and are thus dioecious, a fact that give rise to the species portion of their botanical name. The tree behind cottage 91 in the northeast part of the John Bartram Arboretum at Kendal at Oberlin is a female and is shown in the pictures below. The males that provide fertilization are over the hill in the New Russia Township Park. The flowers of the female have a rose-like fragrance, yielding pods that are 5-10 inches long. The pods and pulp contain the toxin cytisine. This is neutralized by drying and roasting the seeds. [Some Native Americans roasted the seeds to make a hot coffee-like beverage that was also consumed by early settlers - hence the tree’s common name.] Many people prefer male trees to avoid dealing with the pods. In the fall the ripening pods contrast beautifully with the yellow leaves. Native trees can grow 60'-75' high and 50' wide in zones 3-8. It's adaptable to a variety of soils, and tolerates drought and draining wet soil which is alkaline or acidic, clay, or sandy. It does best in full sun. The Kentucky Coffeetree is known to be pest and disease free. The wood, which needs to be dried carefully, is strong, heavy, and highly valued for use in general construction and cabinet work.
The Coffeetree has become rare in the wild. This is because Ice-Age mammals that ate and dispersed the seeds are extinct. The Kentucky Coffeetree also can reproduce by shoots that sprout from the roots to form clonal colonies. In the urban setting this often is not desired and is controlled by clipping or mowing off the new sprouts. This has been done around the tree in our Arboretum. Coffeetrees have taproots that make them difficult to transplant the way we typically move plants grown in nurseries.
Enjoy the beautiful pictures taken of this unique tree in all seasons in our Arboretum and encourage the planting of this uncommon species and its new cultivars.
Anne Helm for the Arboretum Committee
for more information go to: plants.usda.gov and Wikipedia
John Bartram Arboretum Male Kentucky Coffeetree
Top, from left to right: The same tree in the fall and winter. Note the naked winter branches that form the basis of its genus name. Finches enjoy the perches. The deeply fissured scaley bark with narrow ridges is shown next. Middle, slightly immature pods grow to reach 6 to 10 inches in length and contain between 6 and 9 seeds surrounded by a sticky pulp. Bottom, leaves are alternate, bipinnately compound, and reach between 1 and 3 feet in length. The central petiole gives rise to multiple pinnae (or pinules) that are the primary segments of compound leaves. Each pinna has multiple leaflets, the ultimate segments of a compound leaf. Some of the leaf features are also seen well in the top left image.
Photography courtesy of Lyn Cope