Winter Trees and Shrubs: Kentucky Coffeetree

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.

fruits of Kentucky coffeetree (Gymnocladus dioicus)

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.

winter twigs of Kentucky coffeetree

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.

pith of Kentucky coffeetree twigs

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.

mature bark of Kentucky coffeetree

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.

fall foliage of Kentucky coffeetree

More Winter Trees and Shrubs:


The Legacy of a Leaky Dioecy

This is the second in a series of posts reviewing the 17 articles found in the October 2014 Special Issue of American Journal of Botany, Speaking of Food: Connecting Basic and Applied Science.

The Ecological Side of an Ethnobotanical Coin: Legacies in Historically Managed Trees by Nanci J. Ross, M. Henry H. Stevens, Andrew W. Rupiper, Ian Harkreader, and Laura A. Leben

As much as we like to think otherwise, pre-Colombian Native Americans altered the natural landscape in drastic and measurable ways. What we often consider an unaltered, pristine natural area before European colonization, actually has human fingerprints all throughout it. Determining just how deep these fingerprints go, however, is a challenge that requires careful and thorough anthropological and ecological studies.

Many such studies have been done, mostly at the community and ecosystem level. For example, Native Americans used fire extensively as a land management tool. This is how prairies were maintained as prairies. Today, forests in eastern North America that were once dominated by oaks have shifted over to maple dominated forests. This is largely (although not solely) because anthropogenic fires have ceased and wildfires are now suppressed. If fires had never been used as a management tool, would oaks (an important Native American food source) have ever maintained such dominance?

Native Americans participated in the domestication of numerous plant species. Much of this was done by way of – as Charles Darwin termed it – unconscious selection. Rather than selecting specific individuals and breeding them to achieve a desired type, they would simply discard undesirable plants and maintain desirable ones. Much of this selection, especially for woody, perennial species was done through land management techniques – such as fire – as opposed to typical cultivation. The authors of this article, interested in whether or not the “legacy” of this method of selection through land management could be observed today in an individual species, developed a preliminary study to begin to answer this question.

Diospyros – a genus in the ebony family (Ebenaceae) consisting of around 500 species – is mainly pantropical with a few species occurring in temperate regions. One temperate species is Diospyros virginiana – common persimmon – which “has a broad distribution throughout the United States from Connecticut south to Florida and west to the eastern edge of Nebraska.” Persimmons were used and managed extensively by Native Americans; however, they are “now viewed as a rare, weedy, wild fruit tree that is known primarily by hobbyists and wild harvesters.”

Fruits of common persimmon, Diospyros virginiana )photo credit: Wikimedia commons)

Fruits of common persimmon, Diospyros virginiana (photo credit: wikimedia commons)

D. virginiana is a dioecious species, meaning that it produces male flowers and female flower on separate individuals. Despite this, some individuals have been reported bearing both male and female flowers while others have been seen having perfect flowers along with either male or female flowers. Some trees have even been reported to be dioecious one year and then having perfect flowers and/or some combination of male, female, and perfect flowers the next year. This variation from the norm – what the authors call “leaky dioecy” – can either be a result of artificial selection or environmental pressures. The authors hypothesized that “leaky dioecy in D. virginiana is a result of historical selection by Native Americans for trees with copious fruit production.” This preliminary study was designed to see if climate and soil conditions might be the reason for the observed “sex expression.”

Skipping ahead, the authors found “no compelling evidence…to suggest segregation due to environmental factors,” signaling them to “move forward in [their] investigation of potential long-term impacts of historical management on the evolution of reproductive traits in American persimmon without the noise of a strong environmental driver.” The authors go on to discuss challenges in their study, including the length of time since “extensive management” making it hard to “uncover a signal of precontact management” and the limitations of having to rely on herbarium specimens. Either way, it is a worthy study to pursue. Even if it does not reveal the full story of how Native Americans managed persimmons in pre-colonial times, further insight into “adaptive flexibility in reproductive systems of long-lived perennial species” and other interesting things that persimmons might teach us will be well worth the effort.

Characteristic bark of common persimmon, Diospyros virginiana (photo credit:

Characteristic bark of common persimmon, Diospyros virginiana (photo credit: