Spiraea tomentosa var. tomentosa
Inflorescences 300–15,000+-flowered, flowers or fruits 12–20 per cm of branches. Pedicels 0.1–0.5 mm. 2n = 36.
Phenology: Flowering Jul–Sep; fruiting Aug–Oct.
Habitat: Wetlands, woodland borders with moist acidic soil
Elevation: 0–400 m
N.B., N.S., Ont., P.E.I., Que., Conn., Del., Maine, Md., Mass., N.H., N.J., N.Y., Pa., R.I., Vt., Va., W.Va., introduced in n, c Europe.
Forms with white petals have been identified as forma albiflora Macbride; plants with rose petals are assigned to forma tomentosa. The chromosome count of 2n = 36 by J. T. Baldwin (1951) was for forma albiflora.