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Yellowwood

Cladrastis kentukea

Pea Family (Fabaceae)

Introduction: Yellowwood is thought to be our best medium-sized, native flowering tree. Its white, fragrant, pea-like flowers hang in 15-inch-long clusters in spring, and, in some years, the tree offers attractive yellow fall foliage. Yellowwood also has a beautiful framework of branches that provides winter interest, but the tree's multiple trunk habit makes it prone to limb breakage at the crotch. It must be pruned to ensure good branch angles.

Culture: This tree prefers deep, moist, fertile, well-drained loam or moist sandy soil with a medium acid pH. It is hardy in Zones 4 to 8. It will tolerate both high pH and acidic soils. Although it flowers best in full sun, yellowwood does well growing in the forest.

Yellowwood must be pruned to ensure good branch angles, or it will break apart. It should be pruned in summer, as the tree bleeds when pruned in spring. It should be grown with a single leader as far up as possible, and pruned to develop wide-spaced branches that have wide angles to the trunk, as well as a U-shaped crotch. If left unpruned, yellowwood will often fall apart after 30 to 40 years. It has thin bark that is easily damaged, however, so care should be taken when working around it.

Botanical Information

Native habitat: North Carolina to Kentucky and Tennessee. Scattered throughout Illinois, Indiana, Alabama, Mississippi, Arkansas, Missouri and Oklahoma.
Growth habit: Low-branching tree with a broad, rounded crown.
Tree size: Reaches a height of 30 to 50 feet with a spread of 40 to 55 feet. Medium growth rate.
Flower and fruit: Perfect flowers are white, fragrant and pea-like, about 1 inch long and hang in 15-inch-long racemes in mid-May. The tree flowers when it has reached a height of 12 to 18 feet, and produces a larger number of flowers every other year or every third year. Fruit is a flat, thin dehiscent pod, about 4 inches long.
Leaf: Pinnately compound, alternate, up to 1 foot long, with seven to 11 leaflets up to 4 inches long. Leaves are yellowish green when they open in spring, turning bright green in summer, then yellow in fall.
Hardiness: Winter hardy to USDA Zone 4.

Additional information: A prime ornamental characteristic of yellowwood is its low-branching form with a broad, rounded crown of delicate branches. Its slender, zigzagging stems are smooth and reddish brown. The tree's beautiful branch framework adds winter interest, enhanced by its smooth, gray bark.

Yellowwood gets its common name from the yellow color of its heartwood when freshly cut. Cladrastis means "brittle branch." The root bark of yellowwood was used as a dye by early settlers in the southern Appalachians. The tree's wood was once used to make gun stocks. Yellowwood's fruit is a typical legume pod and ripens in the fall.

Botanist Andre Michaux discovered yellowwood in the winter of 1796. There is only one yellowwood species in North America. There are others in Asia. Yellowwood won a Pennsylvania Horticultural Society Gold Award in 1994.