Cephalanthus occidentalis is a shrub to 5 m tall (occasionally taller), stems crooked, bark flaky, dark, young stems speckled with corky, pale dots (lenticels); colonial, probably from root sprouts, often forming dense thickets; leaf scars almost circular, vein scars U or crescent -shaped; stipules linear, persistent, leaving scar across node (Harlow 1946).
Leaves opposite, sometimes in whorls of 3-4, egg-shaped to elliptic, 6-15 cm long, 3-10 cm wide, tip long-pointed, veins pinnate; leaves expand mid-May; winter plant leafless 214 days (Britton 1874).
Flowers cream white, small, radially symmetrical, 4 parted, petals (corolla) fused, tube 0.6-1 cm long, lobes 0.1-0.2 cm long, , tube funnel-shaped, calyx much shorter than corolla; stamens 4, short, arising from inner wall of corolla tube; stigmas globular style 0.5-0.8 cm longer than corolla; flowers in dense, ball-shaped heads, 2-4 cm across, appearing fuzzy from projecting styles, inflorescence stalks 2.5-5 cm long (Seiler 2007), near ends of twigs; blooms July-Aug.
Fruit a dry nutlet, 0.5 cm long, pyramid-shaped, 0.4-0.7 cm long (Radford et al. 1968); dropping into water through fall and winter, Aug.-Jan., dispersed by water. Seeds eaten by ducks and some other birds, twigs eaten by deer and rabbits (Martin et al. 1951).
Wetland status: OBL.
Frequency in NYC: Occasional.
Habitat: Open, undisturbed pond margins and marshes, Saturated soil, freshwater tidal and nontidal marshes, pond edges (Hough 1983). Soil pH 6-8.5. Tolerates concrete debris, soil compaction, flooding (temporary inundation for up to 75% of growing season), often grows in shallow standing water. Very intolerant of shade and drought (Hightshoe 1988). Does not bloom and dies out slowly under dense shade of closed canopy swamp forest.