Kentucky Coffeetree Seeds (Gymnocladus dioicus)

The tree that forgot it lived in the Ice Age. Extraordinary in every season.

Gymnocladus dioicus, the Kentucky Coffeetree, is one of the most distinctive and underplanted native trees in North America, a large, open-crowned hardwood with massive compound leaves, dramatic silver-gray ridged bark, and thick, leathery seed pods that persist on female trees through winter and rattle in the wind. It was once distributed across the eastern United States with the help of mammoths and giant ground sloths that ate and dispersed its toxic pods. Those animals have been extinct for 10,000 years and the tree has barely spread since, a ghost of the Pleistocene waiting for a disperser that never comes back. Its wood is among the most rot-resistant of any North American hardwood. Its winter silhouette, with coarse, irregular branching and a blue-gray cast to the bark, is unlike any other native tree. If you are looking to buy Kentucky Coffeetree seeds or grow this ancient native from seed, this is one of the most botanically interesting trees in the eastern forest.

• Massive bipinnate compound leaves up to 3 feet long, the largest compound leaves of any native tree in eastern North America
• Dramatic silver-gray ridged bark and coarse open branching creating a striking winter silhouette
• Thick leathery seed pods persisting through winter, distinctive and architecturally interesting
• Among the most rot-resistant hardwoods in North America, wood used for fence posts and railroad ties
• A relict of the Pleistocene, dependent on now-extinct megafauna for seed dispersal

Things you probably did not know about the Kentucky Coffeetree

The pods and seeds are toxic to most animals. Kentucky Coffeetree pods contain cytisine, a toxic alkaloid that causes vomiting, diarrhea, and potentially fatal convulsions in dogs, livestock, and humans if consumed in quantity. The toxicity is why no living animal disperses the seeds now that mammoths are gone. The only effective seed dispersal today is water transport along rivers and human planting. The tree has not significantly expanded its range in 10,000 years as a result.

Early settlers roasted the seeds as a coffee substitute. Despite the toxicity of raw seeds, extended roasting at high temperatures destroys much of the cytisine, making the seeds safe to consume. Early European settlers in Kentucky, Tennessee, and Ohio roasted and ground the seeds as a coffee substitute during periods when coffee was expensive or unavailable. The quality and safety were both variable and the practice never became widespread, but it gave the tree its common name.

The wood produces the longest-lasting fence posts of any native tree. Kentucky Coffeetree heartwood has been tested for rot resistance in ground contact studies and consistently outperforms most other native hardwoods, with documented fence posts in service for over 50 years without significant decay. The combination of density, resin content, and natural preservative compounds makes it one of the most practical native trees for farm and property use.

It leafs out later than any other native hardwood and drops its leaves earlier. Kentucky Coffeetree maintains a bare canopy well into late spring, often the last native tree to show leaves in May, and drops them earlier than most hardwoods in fall. This means it has one of the shortest leafy seasons of any deciduous tree in the eastern forest, spending more time as a beautiful architectural bare structure than it does as a leafed-out shade tree.

Growing Details

• Botanical Name: Gymnocladus dioicus
• Stratification: Required, scarification followed by 30 to 60 days cold stratification
• USDA Zones: 3 to 8
• Soil: Adaptable, prefers deep, moist, well-drained soil but tolerates a range of conditions
• Light: Full sun
• Height: 60 to 80 feet
• Spread: 40 to 50 feet
• Growth Rate: Moderate, 1 to 2 feet per year

Plant it for the winter. When everything else goes bare, the Kentucky Coffeetree becomes one of the most interesting structures in the landscape.