Japanese Spiraea (Spiraea japonica)
This attractive bush is a garden favorite, but it seeds itself and can become invasive. It likes a wet location, especially along the banks of a stream. This bush was growing along the Squaw Run in Fox Chapel, where it was finishing up its blooming in the middle of July.
In the horticultural trade, “Spiraea” is often spelled “Spirea.”
Gray describes the genus and the species, which in his time had not gained much of a foothold in North America:
SPIRAEA [Tourn.] L. Calyx 5-cleft, short, persistent. Petals 5, obovate, equal, Imbricated in the bud. Stamens 10-50. Pods (follicles) 5-8, not inflated, few-several-seeded. Seeds linear, with a thin or loose coat and no albumen. — Shrubs, with simple leaves, and white or rose-colored flowers in corymbs or panicles. (The Greek name, from speiran, to twist, from the twisting of the pods in some of the original species.)
Flowers In compound corymbs.
Calyx -tube top-shaped, pubescent.
S. japónica L. f. Stems 1 m. or more high; leaves 7-9 cm. long, glaucous beneath; petals pink to deep rose-color. — Frequent in cultivation, and occasionally escaping, s. Ct. (Graves) and e. Pa. (Introd. from Asia.)