A few years ago, I was on the hunt for a Kentucky coffeetree. I was aware that a few could be found in some of the parks around Boise, but not being familiar with them, I wasn’t sure where exactly to find one or what I was even looking for. One winter while riding my bike to work, I noticed a tree at the edge of a golf course. No doubt I had passed this tree hundreds (if not thousands) of times. What caught my eye were thick, bean-like pods hanging from the ends of branches. They were unlike any other tree fruits I was familiar with. I stopped and, with a little effort, knocked one of the pods free from the tree. When I split it open, I found three or four large, smooth, black seeds inside. Later, I confirmed that the tree was indeed Kentucky coffeetree. Passing by it during any other time of year, it may have never caught my eye – just another deciduous tree with green leaves that, from a distance at least, looks like so many other deciduous trees. But in winter, with several chunky pods hanging from the tips of its stout branches, it really stood out. This is the joy of looking at trees and shrubs in the winter, where features that may otherwise be obscured, become glaringly obvious against the plainness of a winter backdrop.
Kentucky coffeetree (Gymnocladus dioicus) is in the bean family (Fabaceae). It occurs in forests across the eastern and central United States and north into southern Ontario, Canada. It is also planted in urban areas both within and outside of its native range. It is a medium to large tree, averaging 60-70 feet (18-21 meters) high and 40-50 feet (12-15 meters) wide. It generally branches out at around 10-15 feet high and forms a narrow, rounded to pyramidal crown. It is a fairly sparsely branched tree compared to other trees its size, which is much easier to observe in the winter after all of its leaves have dropped.
The winter twigs of Kentucky coffeetree are thick and stubby with few hairs and can be greenish, orange, brown, or deep wine-red in color. They have small, scattered lenticels that are either white, orange, or orange-brown. Their leaf scars are alternately arranged and are heart- or sheild-shaped and very large with 3 to 5 distinct bundle traces. It’s pretty obvious from the leaf scars that Kentucky coffeetree bears a sizeable leaf. These massive, bipinnately compound leaves are demonstrated in this Plant Sleuth YouTube video. Leaf buds are tiny and found directly above the leaf scar. There are usually two of them, one of which is sterile and can be difficult to see. They are round, hairy, olive-colored, and sunken like fuzzy, little craters, although you’ll need a hand lens to really see the hairs (which I highly recommend). The twigs lack a terminal leaf bud. Their pith is rounded, thick, and either orange, brown, or salmon colored. The young bark of Kentucky coffeetree is pale gray and fairly smooth. As the tree ages, it breaks into shallow ridges that run the length of the tree. At maturity, the bark is shades of grey and scaly with long, defined, narrow ridges.
Kentucky coffeetree is dioecious, meaning that there are “male” trees and “female” trees. The tree that I found on the golf course was a “female” tree because it was bearing fruit, which the “males” and certain cultivars won’t have. If there are no seed pods present, you will have to rely on other features to identify the tree; however, when the pods are present, the tree is unmistakable. Its fruits are thick-walled, flat, oval-shaped, smooth, leathery, and orange-brown to black in color. They measure around 5 to 10 inches long and up to 4 inches wide. They are indehiscent and can persist on the tree for more than a year, and even those that fall to the ground can take months or years to break down enough to release the seeds, which have a hard, dark seed coat. Inside the pod, the seeds are embedded in a thick, gooey, yellow-green pulp, which some descriptions call sweet. However, it doesn’t look appetizing enough to try, and considering that the seeds are toxic, I’d be hesitant to consume any part of the fruit without first verifying its safety with a reputable source. That being said, the seeds can be roasted and used to make a coffee substitute and, as long as it’s done correctly, is safe to drink.
Kentucky coffeetree is one of the last trees to leaf out in the spring and one of the first to drop its leaves in the fall. Flowers appear in mid to late spring. The leaves have a pink to bronze color as they first emerge, and in the fall they turn bright yellow before they drop.