Common Name: Kentucky Coffee Tree

General Information

Gymnocladus dioicus is a deciduous tree with an open, sparsely-branched, narrow, rounded crown; it usually grows 18 - 24 metres tall, though there are reports of trees reaching up to 33 metres. The bole usually forms branches from low down; it can be 60 - 100cm in diameter. The plant produces suckers and can form thickets in the wild[, , ].
The tree is harvested from the wild for local use as a food, medicine and source of materials. It is sometimes grown on mine tips in order to restore the soil, and is often grown as an ornamental, the male form being favoured for this because it does not produce seedpods[].
Gymnocladus dioicus does not reproduce well in the wild and population numbers are dropping. The tree has many of the attributes of being a pioneer species and is probably a survivor from a time when megafauna would have eaten the seedpods and transported the unharmed seeds to a new location. There is no natural vector of dispersal for the seed of this tree nowadays, apart from water with which it is not totally well adapted. The tree is more or less restricted to floodplains in the wild, though where it is found at higher elevations it generally thrives but seldom regenerates there by seed[].

Known Hazards

The ripe seed contains hydrocyanic acid. This toxin can be destroyed by thoroughly heating the seed for at least 3 hours at 150°c[].
The seed contains saponins[].
Although poisonous, saponins also have a range of medicinal applications and many saponin-rich plants are used in herbalism (particularly as emetics, expectorants and febrifuges) or as sources of raw materials for the pharmaceutical industry. Saponins are also found in a number of common foods, such as many beans.
Saponins have a quite bitter flavour and are in general poorly absorbed by the human body, so most pass through without harm. They can be removed by carefully leaching in running water. Thorough cooking, and perhaps changing the cooking water once, will also normally remove most of them. However, it is not advisable to eat large quantities of raw foods that contain saponins.
Saponins are much more toxic to many cold-blooded creatures, such as fish, and hunting tribes have traditionally put large quantities of them in streams, lakes etc in order to stupefy or kill the fish and make them easy to catch[].

Botanical References

, ,

Range

Eastern and Central N. America - New York to Tennessee, west to Arkansas and South Dakota.

Habitat

Prefers deep rich soils in bottomlands, deep ravines and moist lower slopes[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	20.00 m
Growth Rate	Medium
Self-fertile	No
Cultivation Status	Ornamental, Wild

Cultivation Details

Gymnocladus dioicus is a very cold-hardy plant, tolerating temperatures down to about -30°c when fully dormant[]. It requires a climate with a hot summer, however, if it is to flower amd set fruit - flowers are seldom formed in areas with cooler summers[].
Requires a sunny position[]. Grows best in a deep rich soil[, ]. Tolerant of a wide range of soils, including poor soils, but dislikes heavy clays[, ]. Tolerates atmospheric pollution, saline soils and limestone soils[]. Established plants are drought tolerant, and can also withstand occasional inundation of the soil[, ].
A very ornamental plant, it is the state tree of Kentucky[, ].
Often very slow growing in cultivation[, ], plants in the wild are somewhat faster and can reach a height of 3.5 - 4 metres in 10 years from seed[].
Trees in the wild seldom live longer than 100 years[].
A dioecious species - both male and female forms must be grown if fruit and seed are required.
Unlike most members of the Leguminosae, his species does not form nodules of nitrogen-producing bacteria on the roots[].

Edible Uses

Seedpod - raw or cooked. The pulp is sweet[, ]. A flavour like caramel[]. The pulp in the seedpods contains antinutritional substances of low toxicity if consumed, causing stomach pains, nausea, vomiting, diarrhoea and an, irregular pulse, that can lead to coma if larger amounts are consumed[]. The pods are 15 - 25cm long and 3 - 5cm wide[, ].

The roasted seed is a caffeine-free coffee substitute[, , , , ]. A bitter flavour[]. Thorough roasting for at least 3 hours at 150°c is necessary in order to destroy the poisonous hydrocyanic acid that is found in the seed[].

Seed - roasted and eaten like a nut[, , ]. The roasted seeds can be eaten like sweet chestnuts[]. The seed contains toxic substances, see notes above.

Medicinal

The pulverised root bark is used as an effective enema[, , ]. A tea made from the bark is diuretic[]. It is used in the treatment of coughs due to inflamed mucous membranes and also to help speed up a protracted labour[]. A snuff made from the pulverized root bark has been used to cause sneezing in comatose patients[].

A tea made from the leaves and pulp from the pods is laxative and has also been used in the treatment of reflex troubles[].

The pulp in the seedpod has been used to treat headaches and fevers[].

The pulp of the wood has been used to treat insanity[].

A decoction of the fresh green pulp of the unripe fruit is used in homeopathic practice[].

Agroforestry Uses:

Trees are planted on the spoil tips of mines in order to stabilize and reclaim the soil[].
The tree has a light, open canopy so does not cast much shade and allows other plants, including grasses, to grow underneath. It is also one of the last trees to come into leaf in the spring, and one of the first trees to drop its leaves in the autumn[, , ], making it a good tree to use for the top canopy of a woodland garden[].

Other Uses

The fruit is high in saponins and is used as a soap[].

The leaves are used as a fly poison and insect repellent[, ]. The leaves and fruit pulp, when mixed with milk, is poisonous to flies[].

A black dye is obtained from the roots[].

The large, very hard, globose seeds are used as beads in necklaces[]. They are used by children in games[].

The heartwood is a rich brown colour, marked or blotched as it were here and there with red.; it is clearly demarcated from the thin band of greenish-white sapwood. It is coarse-grained, without any characteristic odour or taste. The wood is heavy though not hard, strong, very durable in contact with the soil. It must be dried carefully due to a tendency to spliIt, but once dried it is stable. It is easily worked, machines well, finishes to a smooth surface and takes a high polish. A handsome wood, it is very suitable for cabinet work and furniture, and is also sometimes used for construction, fencing etc[, , , , , , , ]. The wood can last for 50 years when used in fencing, though the staple used to hold wire are liable to pull out of the soft wood[].
The wood makes a good fuel, burning well with a good heat, with low amounts of smoke or sparks and a pleasant fragrance[].

Propagation

Seed - best sown in a greenhouse as soon as it is ripe[]. The seed can also be sown in early spring in a greenhouse[]. Scarification and pre-soaking the seed for 24 hours in warm water, especially if it has been stored, will improve germination[]. Make sure the seed has swollen after soaking, soak it again if it has not and, if it still does not swell, try filing away some of the seedcoat but be careful not to damage the embryo. As soon as they are large enough to handle, prick the seedlings out into fairly deep individual pots and grow them on in the greenhouse for at least their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Consider giving them some protection against the cold for their first couple of winters outdoors
Root cuttings 4cm long and 1cm thick in a greenhouse in December[]. Plant the roots horizontally in pots[]. Good percentage.