Kentucky Coffeetree

Gymnocladus dioica

by John Brouwer

A Kentucky coffeetree is well-established between block one and the road. We can thank an early Beaver Creeker for planting this provincially threatened tree over twenty years ago so that we now have a good-sized specimen.

Pioneer legends suggests that the name comes from the seed which Kentucky pioneers used as a coffee substitute. The tree is part of the legume family and the seeds are produced in pods, each containing up to seven seeds. In common with some other legumes, the seeds contain saponins which will make you quite ill when used in quantity. Either pioneers had cast iron stomachs or the legend has little factual history.

The Kentucky coffeetree is rare throughout its Carolinian range. The northern natural limit of its range is southwestern Ontario. There are fewer than 20 natural stands left in Ontario, mainly in Lambton and Essex counties. As the trees require cross-pollination, individual plantings can not reproduce and establish natural stands. And natural stands are isolated, even if some bird or animal would inadvertently move seed, as both a female and male tree are required to reproduce.

Some biologists attribute the very isolated stands of coffeetree throughout the Carolinian zone to seed distribution through its early history. Today coffeetrees have no bird or animal to transport the seed. Squirrels know not to eat the seed because it is poisonous to them and neither do birds. However very large animals like elephants are not affected by legumous toxins, even in quantity, and seeds pass unharmed through their digestive tract. The theory is that at the time of the mastodons coffeetrees became widely distributed within the forests of eastern North America. With the extinction of the mastodons, coffeetrees lost their distribution agent, leaving only scattered stands which can not migrate beyond their isolated islands. Whatever you make of this theory, you can be sure that our Kentucky coffeetree was not planted by mastodon dung.

In this area coffeetrees grow to 60-70 feet with a trunk diameter of up to 3 feet.

Coffeetrees are unique in being among the last tree in the forest to leaf out in the spring and the first to drop its leaves in the fall. The tree spends up to nine months of the year without leaves. It produces huge leaves, up to one meter long and 60 cm wide, each composed of 40 or more leaflets set on individual leaf stems.

Biologists are challenged in understanding why the coffeetree would expend the energy creating such huge leaves every year and dropping them so early before the leaves could maximize their photosynthesis over a normal growing period.

Contrary to the logic inherent in its name, Kentucky coffeetree is no longer the state tree of Kentucky. That honour is reserved for the yellow poplar (tulip tree), although it took almost twenty years of sometimes heated debate in the legislature before coffeetree lost this status in 1994.

Coffeetrees are an excellent tree for passive solar construction. Because its large leaves emerge late in the spring and drop early in the fall, nearby buildings retain solar heat gain in mid-spring and fall but the extreme summer sun is shaded by the mottled canopy, which provides good shade but still allows indirect sunlight.

Native Americans used the pulp made from the wood to treat insanity. A tea from the leaves and pulp was used as a laxative.

Coffeetrees have had few commercial uses because the species is so scattered. Earlier the lumber was used for railway ties and fence posts as the wood is rot-resistant in contact with soil.

Under Ontario's Endangered Species Act 2007, the Kentucky coffeetree is listed as an endangered species. The Act prohibits harming or killing the species. There are two coffeetrees growing in the developable block of land between Pine Ridge and Westmount Roads. It will be interesting to see how RIM proceeds with developing this property while protecting these trees.