Finding a Kentucky coffee-tree (Gymnocladus dioica) growing in the wild in Ontario is rare. Its deceasing presence led the Government of Ontario to list the species as threatened in 2008 (read why). But because it’s tolerant of urban conditions and has few pests, it’s becoming a popular street tree in southern Ontario.
Kentucky coffee-tree grows best in moist, well-draining and organically rich soil, but it can be grown in sand, loam or clay. It can withstand juglone from black walnut trees, compacted soil and drought conditions. It is also tolerant of urban pollution and winter road and sidewalk salt.
Reaching up to 90 centimetres long, the leaves on Kentucky coffee-tree are some of the largest leaves of any Ontario tree. These compound leaves are divided into many small, bluish-green leaflets. They are some of the last leaves to emerge in the spring and the first to drop in the fall, but not before turning a brilliant yellow.
While some trees will have flowers with both male and female parts, this is rare. Most trees are dioecious meaning they have flowers with only male parts (stamens) or female parts (pistil), but not both. The female clusters are larger than the males, but both consist of small, white, fragrant flowers that bloom after the leaves are out.
The flowers are visited by many bees, butterflies and hummingbirds searching for nectar. As long as a male tree is nearby for cross-pollination, the flowers on a female tree will produce large flat seed pods that will cling to the tree providing winter interest. The seed pods are too tough for today’s mammals to eat. So unless scientists are able to bring back the mastodon, they will need to be tidied up in spring.
The tall, straight stature of the Kentucky coffee-tree and unique rough-textured bark make it a great focal point for any yard. If you have space for more than one tree, pair it with other hardy urban trees, like common hackberry or silver maple, or create layers by adding shrubs like cockspur hawthorn or fragrant sumac.
Note that the Ontario Government warns against purchasing and planting ornamental trees from non-native stock because “their genes may contaminate the locally adapted gene pool” and contribute to the decline of the species.
Photo: Leonora (Ellie) Enking