This herbaceous perennial has alternate, simple leaves on arching stems.

The flowers are pink or white, borne in dichotomously branching cymes from late summer through fall in USDA U.S. Hardiness Zone 7.

It can overwinter well in hardiness zone 9a in southwestern Japan as tuberous roots or bulbils (bulbils are formed in axils).

Above-ground parts of this plant eventually die as temperature lowers.

alba have gained the Royal Horticultural Society's Award of Garden Merit.