First cultivated in 1870 as an ornamental shrub in the northeast and now naturalized across much of the United States, Japanese spiraea (Spiraea japonica) is native to China and Korea as well as Japan. A perennial shrub of the Rose family, it is also called Japanese meadowsweet. Maximum growth is to between four and six feet, both high and wide. Growth is also basically upright, on slightly hairy stems, with alternately oval leaves. Attractive pink blooms cluster at stem tips. Typically, Japanese spiraea is used as a ground cover, in foundation plantings, as hedges, and as screens.

Growing Conditions and Patterns

Happiest with a soil heavy in rich moist loam, such as organic mulch or manure, Japanese spiraea tolerates a variety of soils. It grows in full sun and partial shade. Full sun encourages dense foliage and blooms. Drought tolerant, spiraea needs generous rainfall during the growing season, but also excellent drainage. Most frequently seen along the East Coast and into the Midwest, spiraea does well in USDA zones four through eight, and does best with a distinct winter season.

Once established, it forms dense stands and chokes out native plants. Clearly, spiraea is tolerant of a variety of soils and growing conditions. Most often, however, spiraea is found along stream beds and rivers, the edge of woods, and power line right of ways. The Plant Conservation Alliance includes spiraea on its list of Alien Invaders. Damp temperate areas are especially vulnerable.

Spiraea seeds last for years in the soil, making control difficult. It can be controlled by repeated mowings, but it is not easily eradicated. Repeated cuttings are necessary to exhaust its reserves. Considered invasive by the National Park Service, Japanese spiraea takes over disturbed areas readily, moving into forest areas, open lots, and many other environments.