Sunday, November 25, 2007

Landscape - Recommended Plants for Kent County: Kentucky Coffeetree

Kentucky Coffeetree, Gymnocladus dioicus
Photo from the University of Minnesota Agricultural Experiment Station
This is a continuation of a series on recommended plants for Kent county landscapes. Kentucky coffeetree is a very trouble free tree that can be used as a replacement for Norway maple. The following is information on this species.

Kentucky Coffeetree, Gymnocladus dioicus

Kentucky coffee tree (Gymnocladus dioicus) – 60-75’ with a narrow oval crown that tolerates dry soil and urban conditions, short-lived fall color but great bold winter structure.

This is a medium-growing tree that will reach a height of about 70 feet while spreading 45 to 60 feet. The state tree of Kentucky should be used more often because it is adaptable to many soils, has interesting bark and grows with an open canopy allowing light to penetrate to the ground for adequate turf growth beneath the canopy. The coarse branch texture in the winter is also quite unique, forming an interesting silhouette of only several large branches. Large seed pods hang on the tree in the winter but can be a litter problem when they fall in the spring. They are very hard and can be ‘shot’ from a lawnmower running over the fruit. Male trees are sometimes available and they do not set fruit, but this is often unreliable. The seeds (in a 5 to 10- inch-long pod) and leaves may be poisonous to humans. The pod contains seeds which used to be roasted as a coffee substitute. The leaves are bipinnately compound and can be up to 18 inches long, resembling walnut.

The trunk normally grows straight up through the crown and is very strong. Branches grow at wide angles to the trunk and are usually well-spaced along the trunk. This configuration adds to the durability of the tree. Be sure that major limbs are kept at less than about half the diameter of the trunk to ensure that they remain well-attached to the tree. The crown is round or oval in youth, becoming more upright and oval with age. Some people object to the sparse branching when this tree is young, but some pruning to create more branches can help. Any shortcomings of the tree are made up by the almost total lack of insect or disease problems. Lawns grow well beneath the tree due to the light shade cast by the thin, open canopy.

Kentucky Coffeetree is well-adapted to urban soil and could be used more often and, like most trees, does best when provided with irrigation until well established. Amazingly tolerant of drought and poor soil once established although it is native to rich bottomland soil. Used as a street tree in some communities. Be careful using the tree in a lawn since the pods could become projectiles from mowing equipment. Male cultivars without fruit are available to avoid this problem. These will be well-suited for planting along streets. Propagation is by seed, or grafting male plants. There are no pests or diseases of major concern.

Information from the Plants for a Liveable Delaware publication and from the University of Florida Cooperative Extension fact sheet Fact Sheet ST-287 by Edward F. Gilman and Dennis G. Watson.

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