Rumex hastatulus is a perennial herb to 1 m tall from a thick, woody root; stems branched from base Stipule (ocrea) membranous sleeve-like around stem above leaf stalk (Flora of North America 1993+).
Leaves alternate, mostly basal, long-stalked, (much like those of R. acetosella), narrowly arrow-shaped, with two narrow, divergent basal lobes, often unequal, central lobe much larger, oblong, narrow. See Flora of North America (1993+).
Flowers greenish to reddish, sexes on different plants (dioecious), male flowers to 0.15 cm, female flowers with appressed edges of petals (valves) forming wings, valves broadly heart-shaped, base lobed, tip rounded; inflorescence to 30 cm long.
Fruit dry, 1-seeded to 0.35 cm long; seeds brown 0.15 cm; Blooming and fruiting June-Aug.
Wetland status: UPL.
Frequency in NYC: Rare, NYS Endangered (USDA, NRCS 2010).
Habitat: Sandy soil of coastal plain.