Culture
Easily grown in average, medium moisture, well-drained soils in full sun. Appreciates some light afternoon shade in hot summer climates. Tolerates a wide range of soils. Remove faded flower clusters as practicable (light shearing is an option) to improve plant appearance. Flowers on new wood, so prune in late winter to early spring if needed.
Noteworthy Characteristics
Spiraea nipponica, commonly called spirea, is a dense, upright, mounded, deciduous shrub that typically matures to 5-8’ tall with a slightly larger spread. It is native to the island of Shikoku, Japan. Obovate to elliptic leaves (to 1 1/4” long) are dark green above but blue-green beneath with round toothed apices. Foliage turns a minimally attractive yellow in fall. Tiny white five-petalled flowers in rounded hemispherical clusters (corymbs) cover the foliage in late spring to early summer (late May to June). Flowers are attractive to butterflies.
Var. tosaensis is more compact than the species, typically growing in a rounded form to 3-4’ tall and as wide with oblanceolate leaves and slightly smaller flowers.
Genus name comes from the Greek word speira meaning wreath in reference to the showy flower clusters seen on most shrubs in the genus.
Specific epithet refers to this shrub as being a native of Japan.
The popular shrub in this species which is most frequently sold in commerce is ‘Snowmound’ which is typically listed as a cultivar of either the straight species or var. tosaensis. Michael Dirr asserts that ‘Snowmound’ is synonymous with var. tosaensis (hort.).
Problems
No serious insect or disease problems. Susceptible to many of the diseases and insects that attack other rose family members, including leaf spot, fire blight, powdery mildew, root rot, aphids, leaf roller and scale.
Uses
Specimen or group for rock gardens. Mass or group in shrub borders. Low hedge for paths and walkways. Incorporates well into foundation plantings.