Spiraea glomerata Rafinesque; S. parvifolia Rafinesque

Inflorescences 300–15,000+-flowered, flowers or fruits 12–20 per cm of branches. Pedicels 0.1–0.5 mm. 2n = 36.

Flowering Jul–Sep; fruiting Aug–Oct. Wetlands, woodland borders with moist acidic soil; 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.