The Kentucky Coffee Tree, Gymnocladus dioicus, is a rare tree, remarkable for the size of its leaves and the stoutness of its twigs. There are two examples in Dulwich, one in the Picture Gallery garden (adjoining College Gardens), the other in Dulwich Park (set back from the north-eastern section of College Drive). There is also a good example in Brockwell Park, towards the old Hall at the top of the hill, now a café.
The huge size of the leaves - up to a yard long - makes them one of the largest of all broad-leaved trees. Their size is not immediately obvious, however, because they are doubly compound i.e. each leaf is divided into primary segments which are themselves divided into secondary segments. In the case of the Kentucky Coffee Tree there can be 140 leaflets in a single leaf. Leaves appear late with the leaflets flushing bright pink at first. Their autumn colour is a clear bright yellow. Leaf fall is early and it is this short leafy season, coupled with the fact that the foliage even when present is mainly towards the end of the branches, that gives rise to the first part of its scientific name: Gymnocladus means ‘bare branch’.
The stout twigs are best observed during the long leafless period, when the whole tree takes on a rather gaunt appearance. They are among the stoutest of all broad- leaved trees, particularly when account is taken of their solid pith - most trees with thick twigs, the walnut for example, have chambered pith. After leaf fall, and before the winter winds do their work, many of the yard- long needle-like leaf stalks still remain attached to the twig, which can give the tree a rather a rather crazed and spiky appearance.
The tree is native to rich woodlands in central North America, especially Kentucky. It rarely flowers in our relatively cold climate. The fruit is a pod, quite modest in size for a leguminous tree. The seeds were used by early European settlers as a coffee substitute, hence the common name. A scan of websites reveals that the opinions of those who have tried it in recent times range from “like coffee with a touch of chocolate” to “like espresso bitter” and “akin to mud”.