Growing a Kentucky Coffeetree from Seed

Kentucky Coffeetree is an attractive tree which is easy tree to grow from seed, if you know a couple of tricks. Imagine how impressed your friends and neighbours will be in ten years’ time, when you can point up to the top of a tree and say “I grew that from a seed!”

Coffeetrees are native to Kentucky but spread as far as southern Ontario. They are sometimes planted in parks and as shade trees in gardens, as they have attractive compound leaves, an interesting sparsely branched silhouette and an deeply creviced bark.

Distinctive bark

The first challenge is to find a source of seeds. They can be bought from Sheffiled’s, but it is better if you can find a local tree. Look for trees with seed pods still attached in March or April when the branches are still bare. Search the ground underneath the tree or shake the branches gently.

Sparse branches, ladened with seed pods in March

Break the pods open and find the black seeds inside along, with some sticky greenish gunk. Depending on the size of the pod there will be one to six seeds inside it.

Seed in pod

After washing the seeds, you need to break through the thick seed coat. In the past mastadons used to feed on the seeds (which are poisonous to other species, including humans, unless they are well cooked). The seed coat was broken up by their stomach acid. Modern nurseries use sulfuric or nitric acid to get the same effect. However, if you do not have a pet mastadon  and do not keep powerful acids in your garage, you can achieve the same effect by sanding the seeds until a paler material inside the seed coat is visible, then soak the seeds in water for 24 hours. That makes them look very straggly and untidy, but that is normal.

Seed after sanding

Plant the seed 1 cm (1/2 inch) deep in good potting soil indoors in March or April or outdoors in May. They will take about a week to germinate and rapidly develop into seedlings which are about 10 cm ( 4 inch) high. However, they are very vulnerable to cold temperatures. Remember that their home is Kentucky! They need to be protected, not only from frost, but also from any cold temperature. Do not move them outside until the might-time temperature is above at least 5 centigrade (40 CF).

Six weeks old

The seedlings can be planted outside as soon as the weather is warm enough, or they can be grown on until the fall and then planted out. Do not be alarmed if they take a long time to leaf out the next spring, as the latin name, gymnocladus, means “naked banch”  (from the Greek γυμνὀς, gymnos, naked + κλάδος, klados, branch). The leaves only appear in late spring, and drop early in the fall.

Still life: A six week old seedling set against a paint-speckled workbench. This specimen only has four leaves, but each leaf is made up of many leaflets.

The tree grows quite rapidly. It flowers in spring time, but the flowers are greenish-white and not very conspicuous.