Osmorhiza claytonii is a perennial herb to 1m tall from thick roots, aerial parts without odor, stem hairy.
Leaves alternate, few, the upper stalkless (sessile), the lower stalked, base wide, clasping stem; blade 2-3 times compound, 10-30 cm long, hairy, leaflets 1.5-9 cm long, 1-4 cm wide, egg-shaped, margins blunt-toothed to lobed, winter rosette leaves often with pinkish stalk.
Flowers white, small, radially symmetrical, 5-parted, petals free, sepals none; stamens alternating with petals; ovary inferior, 2-parted, each part with one style, shorter than petals; fertile and sterile (staminate) flowers mixed; producing nectar; inflorescence sparse, compound-umbrella-shaped, primary rays 3-5, each 2-5 cm long, bracts at base of the primary rays 1-3; secondary rays 5-18 each with one flower, bracts at base of secondary rays 3-5, ca 0.4 cm long; inflorescence stalk 5-15 cm long (Radford et al. 1968); blooms May-June; visited by butterflies.
Fruit dry, in pairs, parts held together by hair-thin stalks; fruit bristly-ribbed, blackish, linear, 1.5-2 cm long, tip with persistent style to 0.15 cm long, base forming a bristly tail; each part 1-seeded; fruits June-Aug. dispersed by clinging to fur or clothing; fruit often persistent on old plant until the following spring; seeds germinate the first or second spring after maturation (Pavek 1992).
Wetland status: FACU-.
Frequency in NYC: Infrequent.
Habitat: Moist woods, occasional in urban parks, acid soils. Increases in forest gaps where light and moisture are more available (Moore and Vankat 1986). Dispersal to and establishment in new sites in successional forest, contiguous to old regrowth stands has been calculated at a rate of 1.50 m/yr (Matlack 1994). Winter plant fragile, soon fallen above winter rosette (Levine, 1995).