Rumex crispus is a perennial C3 herb (Pooter et al. 1990), from a large taproot, stem to 1.5 m long, ribbed, encircled by old leaf scars, unbranched below inflorescence; winter plants erect, dark brown, basal rosette large (Levine 1995). Stipule (ocrea) membranous sleeve-like around stem above leaf stalk (Flora of North America 1993+).
Leaves alternate, lower and basal leaves large, 15-30 cm (Uva 1997), usually quite narrow, tapered to base and tip, rounded at base, edges curly, leaves become reddish through growing season; basal leaves of the next year emerging after fruit of the present year as ripened, persistent in winter, dying as flowering stalk developes in late spring; stem leaves smaller. See Flora of North America (1993+).
Flowers tiny, greenish, becoming brown in fruit; sepals 3 narrow, petals three, bract-like, broadly egg-shaped, 0.4-0.5 cm, margins entire, appressed to one another as wings, lower part of mid vein of 1-3 petal(s) forming a bulbous tubercle along its lower half; one tubercle often larger than the other two, individual fruit stalks with swollen “joint” about 1/3 way above base; inflorescence branched, large; blooming May-July (Hough 1983); appears to bloom well before the other large Rumex species.
Fruit 1-seeded; dark brown, persistant petals with paler tubercle(s), enclosing 3-sided (trigonous) seed; fruiting June-Sept.(Hough 1983); ripens in summer but persistent on inflorescence into late fall or winter, dispersed during winter, seed germination during spring, requires light, seeds can persist in soil many decades (Baskin and Baskin 1978). Seeds eaten by many birds and small mammals, leaves eaten by mammals (Martin et al. 1951).
Wetland status: FACU.
Frequency in NYC: frequent.
Habitat: A weed of open areas, roadsides, edges, fill.
Notes: Dyes made from roots (Hough 1983). Leaves contain oxalic acid (Wikipedia.2017).