Japanese Pagodatree, Styphnobilobum japonicum
Looking for a tough, unusual tree to diversify your urban forest? One with character and multi-season interest? Give the Japanese pagodatree, sometimes called the Chinese scholar-tree, a look. Japanese pagodatree has been extensively planted near temples and shrines in eastern Asia for centuries. It is native to China and Korea, but—oddly enough, considering both its common and botanic names—not Japan. The tree was introduced to the western nursery trade in 1747.
Those of us who know the tree as Sophora japonica should be aware that botanists have recently renamed the tree Styphnolobium japonicum to differentiate it from trees of the genus Sophora. The roots of Sophora species form associations with soil bacteria to fix nitrogen like most members of the Fabaceae family. Recent scientific studies, however, show that Japanese pagodatree is one of the few trees in the extensive Fabaceae family that does not fix nitrogen in the soil. Who knew?
The Japanese pagodatree produces large, very showy panicles of creamy white pea-like flowers over several weeks in mid to late summer, a time when most other flowering trees are done with their show. Dark green compound leaves provide dappled shade through summer, becoming yellow in fall. Bark develops a rugged look similar to oak as the tree matures, offering winter interest. Bean-like pods are 3 to 8 inches long, and are retained on the tree through winter, an additional seasonal texture. The roots tend to be fibrous and deep, unlikely to affect nearby hardscape.
Japanese pagodatree is not fussy about soil or water, and is not susceptible to common pests and diseases. Like many trees, it performs best in locations with full sun and moist, well-drained soils although it will withstand heat, drought, compacted soils and pollution once established. No matter where you live in Washington, the pagodatree is an excellent street tree candidate where there is enough space for full canopy development. Young pagdoatrees do have a reputation for ‘floppy’, non-upright leaders, however a little firm pruning discipline will help young trees develop good structure to prevent this. Recently developed cultivars such as ‘Regent’ express less of this tendency.
This lovely tree achieves a round-headed silhouette approximately 45 feet in height and about the same in spread, depending on the cultivar. Commonly available cultivars include Millstone (S. japonicum ‘Halka’); Regent; Pendula, a weeping form; and Princeton Upright, a compact upright form. The combination of urban hardiness and a wide range of genetic variation in the species suggests this tree deserves further study to develop desirable forms for urban planting locations.
Channel your inner scholar by including this very distinctive and handsome tree in your next planting project!