Arboretum: Gymnocladus dioica, Kentucky coffeetree
As fall approaches, trees are developing nuts, cones and seed pods. Hard to miss are the thick brown pods, 4 to 8 inches in length, hanging on the Kentucky coffeetree, Gymnocladus dioica. The round seeds inside resembled coffee beans to early settlers who roasted them in a poor attempt to approach the taste of that beverage. The pulpy substance surrounding the seed inside the pod contains an alkaloid and the raw seed itself contains toxic cytisine. But Native Americans used the roasted seeds and powdered root both as food and medicine.
This native tree is found from southeastern Canada through New York and Pennsylvania into the central Midwest. Its coarse silhouette and open branching can reach 75 feet high and 30 to 50 feet wide. At Haverford College, a massive specimen stands to the right of Sharpless Hall on the edge of Founders Green.
Gymnocladus means naked branch; the tree’s winter silhouette is rugged-looking and easily identifiable. Dioica means it is dioecious; there are separate male and female trees. The greenish white flowers are hard to see in spring, The tree leafs out late, with rows of small leaflets making up the gigantic double compound leaves up to 36 inches in length. The result is filtered shade underneath the canopy, much like a honeylocust. Gymnocladus dioica is not common in the wild, where it grows best in moist river valleys. Yet it tolerates drought and adapts well to urban conditions with a range of soils.
Because of its size and perhaps the messiness of dropped seed pods, this tree is not often found in the home landscape. Give it a location in full sun and it will grow fast when young, slowing down in later years. The flower nectar is a good food source for bees and wasps.