Threeleaf Foamflower

Tiarella trifoliata is a perennial dicotyledonous herb that flowers in the late spring. The flowers are bell-shaped, white and solitary forming an elongated, leafless panicle. The calyx lobes are 1.5–2.5 mm and petals are 3–4 mm. Basal leaves are 15–80 mm long and up to 120 mm wide, trifoliate or palmately 3- to 5-lobed. Cauline leaves are infrequent and much smaller. The typical variety of Tiarella trifoliata (var. trifoliata) has petiolate leaves with three leaflets per leaf (i.e., trifoliate). The cut-leaved foamflower (var. laciniata) also has trifoliate leaves with petioles, but unlike the typical variety, it has deep lobes more than half the length of the leaflet. The one-leaf foamflower (var. unifoliata) has sessile, simple leaves (rarely trifoliate).

In western North America, Tiarella trifoliata prefers shaded, moist, sometimes dense woods up to 1,900 m (6,234 ft). It ranges from northern California through western Canada northward to Alaska, and eastward to Montana. Within this region, the varieties of T. trifoliata have overlapping ranges:

Tiarella trifoliata var. laciniata: British Columbia; Oregon, Washington Tiarella trifoliata var. trifoliata: Alberta, British Columbia; Alaska, California, Idaho, Montana, Oregon, Washington Tiarella trifoliata var. unifoliata: Alberta, British Columbia; Alaska, California, Idaho, Montana, Oregon, Washington T. trifoliata var. trifoliata and T. trifoliata var. unifoliata range north to Alaska, while T. trifoliata var. laciniata only ranges as far north as Vancouver Island in British Columbia.