Description & Overview
Gymnocladus dioica, the Kentucky Coffeetree, is a slow-growing deciduous tree in the bean family. Somewhat of an ugly duckling in youth, this tree will mature into a graceful swan. Its bluish-green compound foliage gives a lacy appearance in summer. The bark adds further interest, with rough-textured grayish-brown scaly plates and irregular furrows.
Kentucky Coffeetree is more narrow and upright in youth but grows quite large over time. With age, its canopy becomes more of an irregularly open oval with prominent ascending and horizontal branches. Understanding the bipinnately compound foliage of Kentucky Coffeetree is key when identifying this tree. It has the largest leaf of any tree in northern climates, reaching nearly 3 feet long and having as many as 100 separate leaflets. Individual leaflets can have 6-14 pairs of subleaflets. Don’t mistake the leaflet for the entire leaf!
Kentucky Coffeetree is an excellent choice as a shade or street tree, or landscape specimen. It is tolerant of various unfavorable growing conditions, making choosing a suitable planting location easier. Kentucky Coffeetree is tolerant of drought, seasonal flooding, salt, and urban pollution.
Kentucky Coffeetree is a dioecious species, meaning there are separate male and female plants, although some individuals can have perfect flowers, meaning they have both male and female parts. Fertile flowers are replaced by leathery seedpods, which mature in fall and often persist on the tree throughout winter. The seedpods are a dark reddish brown and about 3-6″ long. Each seedpod contains 3-6 seeds immersed in a sweet gelatinous substance.
The flowers are cross-pollinated by numerous pollinators such as bumblebees, long-horned bees, butterflies, and hummingbirds. Caterpillars from numerous moth species have been observed feeding on the foliage. Mammalian herbivores tend to avoid eating Kentucky Coffeetree because the fruit leaves, seeds, and pulp are poisonous and toxic to livestock, humans, and pets.
Gymnocladus dioica contains alkaloid cytisine which causes low toxicity if eaten.
Kentucky Coffeetree prefers full sun and organically rich soil that’s well-draining, although it adapts well to urban conditions. When considering its cultural tolerances, Kentucky Coffeetree should be on the list of “tough” trees. Thanks to its toughness and adaptability, Kentucky Coffeetree has been utilized in planting on old mine spoils for soil reclamation and stabilization.
Fallen leaf stalks and pods require some cleanup. Pruning is best done during the dormant season.
We invite you to check out the Arborist For Hire lookup at the Wisconsin Arborist Association website to find an ISA Certified Arborist near you.
Due to the tree’s toxic plant parts, there’s little wildlife that uses Kentucky Coffeetree as a food source. Thankfully, there aren’t any insects that cause significant damage to the plant. There are also no severe disease issues. Thanks to this tree being virtually pest free, we often see it as an alternative to ash and elm, which insects and diseases have ravaged.
The genus name Gymnocladus is made up of two words, ‘Gymnos,’ the Greek word for “naked,” and ‘klados,’ which is Greek for “branch.” The leaves are late to emerge in spring and early to fall in autumn, leaving the tree branches naked for much of the year. The specific epithet dioica (alternatively spelled ‘dioicus’) refers to the tree’s dioecious nature.
Gymnocladus dioica is a legume family (Leguminosae) member, of which many species are noted for their ability to fix nitrogen. When plants are considered nitrogen fixers, they have roots colonized by certain kinds of bacteria that extract atmospheric nitrogen and convert or “fix” it into a form that becomes available to the plants and the bacteria themselves. This symbiotic relationship is nitrogen fixation. Kentucky Coffeetree can fix nitrogen, although at much lower rates than most plants that find themselves in the legume family.
Native Americans and early pioneers roasted and ground the seeds to brew a coffee-like beverage, although many considered this an inferior substitute due to the absence of caffeine. Supposedly, the roasting process removes the dangerous toxins. It is said they must be roasted at 150°F for at least three hours to be safe for human consumption.
Native Americans also used parts of Kentucky Coffeetree for various medicinal purposes. The Omaha were said to have used the outer covering of the root to treat hemorrhaging. It noted that the fruit’s pulp was used to combat fevers and headaches. It was also used as a laxative. George Washington’s diaries from the late 1700s contain the first known account of the name “coffee tree” being used. Thomas Jefferson also acquired Kentucky Coffeetree seeds from General George Rogers Clark in 1783, which he planted at Monticello.
Kentucky Coffeetree is a tough plant, making it a great choice when planting in tough sites. You should pair it with other similarly durable plants.
Looking for a seedless version of Coffeetree? Check out Espresso™ Kentucky Coffeetree.