Native to (or naturalized in) Oregon:
- Deciduous shrub, may grow to between 20 and 100 cm (~8 inches to 3+ ft) tall, stems brown, glabrous to finely and sparsely hairy. Leaves alternate, simple, ovoid, 1–5 cm long, margin toothed near tip and sides but not at the base, leaf surface thin, light green, with or without hairs, turn yellow in fall; petiole less than 3 mm long. Flowers small (~ 2 mm), rose-pink, in flat-topped, terminal clusters (corymbs), very showy. Fruit small, 5 valved follicle.
- Sun to light shade, moist, well-drained soil.
- Hardy to USDA Zone 3? Native range from southwestern British Columbia to California, at elevations between 2,000 and 11,000 ft (~600-3,300 m) on inland mountain ranges, especially in moist, rocky areas.
- Two forms are recognized:
- Spiraea densiflora subsp. densiflora: more or less hairless (glabrous).
- Spiraea densiflora subsp. splendens: plants finely pubescent on flower clusters and lower leaf surfaces. Also named Spiraea splendens.