Japanese Spiraea (Spiraea japonica)

Spiraea japonica is one of several Spiraea shrubs with alternate, simple leaves, on wiry, freely branching, erect stems. Stems are brown to reddish-brown, round in cross-section and sometimes hairy. The shrub reaches 1.2 m to almost 2 m in height and about the same in width. The deciduous leaves are generally an ovate shape about 2.5 cm to 7.5 cm long, have toothed margins, and alternate along the stem. Clusters of rosy-pink flowers are found at the tips of the branches. The seeds measure about 2.5 mm in length and are found in small lustrous capsules.

It is naturally variable in form and there are many varieties of it in the horticulture trade. So far, nine varieties have been described within the species.

Spiraea japonica is a deciduous, perennial shrub native to Japan, China, and Korea. Southwest China is the center for biodiversity of the species. It is naturalized throughout much of the Northeast, Southeast, and Midwest areas of the United States, and parts of Canada.

Habitat: A common habitat for S. japonica in general seems to be in riparian areas, bogs, or other wetland habitats. It is found growing along streams, rivers, forest edges, roadsides, successional fields, and power line right-of-ways. It prefers full sun, but can tolerate partial shade. It prefers lots of water during the growing season; however, it cannot tolerate saturated soils for extended periods of time. It prefers a rich, moist loam, but it can grow in a wide variety of soils, including those on the alkaline side.

Uses: Spiraea japonica was introduced in North America as an ornamental landscape plant and first cultivated in the northeastern states around 1870.


Photographic Location: Rock Island State Park in Middle Tennessee.

Numerous cultivars have been selected for garden use. The tall forms may be grown as hedges, low screens, or foundation shrubs. The low-growing forms can be used as ground cover or in borders. Spiraea japonica has been used as traditional medicine by native people, and extracts from the plants were found to be bioactive.