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.
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.
'Snowmound' is a dense, upright, compact, mounded cultivar which typically grows to 2-4' tall with a similar spread. Profuse white flowers in small corymbs cover the arching stems of this plant in late spring. Flowers and leaves all appear on the same side of the arching branches. Flowers are attractive to butterflies. Narrow, dark blue-green foliage. A Royal Horticutural Society of Great Britain Award of Garden Merit plant.
Problems
No serious insect or disease problems. Susceptible to many of the diseases and insects that attack other members of the rose family, including leaf spots, fireblight, powdery mildew, rots, aphids, leaf roller and scale.
Uses
Effective in borders, foundation plantings or hedges.