Cladrastis platycarpa

Japanese yellowwood

While the flowering tree market has long been monopolized by dogwoods, flowering cherries, and crabapples, there are other options available for discriminating gardeners. One such unusual plant is the Japanese counterpart to our native yellowwood. Cladrastis platycarpa is a medium-sized tree occurring in the mountains of Japan on the main island of Honshu and the large island of Shikoku. In some literature it has been described as a small tree but it can grow quite large in time. In landscapes, a height of 30' to 45' in 20 years would be a reasonable expectation.

It is a fine tree throughout the seasons bearing long, 8" to 14", medium-textured pinnate leaves made up of 7 to 13 alternately arranged leaflets which are each 2" to 4" long. In mid to late spring between late April and early June, panicles of white pea flowers with a yellowish blotch on the two upturned or keel petals dance in the breeze backed by the medium green foliage. The fruit are flat and winged pea pods (platycarpa means flat fruit) which are pale green and quite attractive against the darker foliage. Fall color is variable but can be brilliant gold in a good year, and the smooth, gray bark is lovely all year but especially during the winter.

The plant is similar to our native P. kentuckea but the Japanese tree is smaller in all aspects including flowers and ultimate size. The somewhat fuzzy, yellow-brown calyces which hold the flowers of the Japanese species also serve to distinguish it from the smooth green ones of our native. Other key differences are the broader leaflets and more pendulous panicles of the native yellowwood.

There are two plants growing at the JCRA. Both are close together just to the east of the live oaks by the pedestrian entrance. They have been in the garden for quite a while but were crowded between the oaks and the old Leyland cypress hedge before it was removed. The low light and tight quarters certainly kept them from growing as quickly as they would in a better spot. They are best utilized in rich soil in full sun with adequate summer moisture but are quite drought tolerant once established.