Plants annual or short-lived perennial, glabrous, with vertical rootstock. Stems solitary or several from base, erect or ascending, branched in distal 2/ 3 (in inflorescence), 10-40(-45) cm. Leaves: blade obovate-oblong, ovate-lanceolate, oblong-lanceolate, or lanceolate; 2-6(-10) × 0.5-2 cm, base hastate (with spreading lobes), auriculate, or occasionally without evident lobes, margins entire, flat, apex obtuse or subacute. Inflorescences terminal, occupying distal 3 of stem, usually lax and interrupted, narrowly paniculate. Pedicels articulated in proximal part, filiform, 1.5-2.5(-3) mm, articulation indistinct or slightly swollen. Flowers 3-6(-8) in whorls; inner tepals orbiculate or broadly ovate, 2.5-3.2 × 2.7-3.2 mm, base broadly cordate or rounded, apex obtuse or subacute; tubercles absent or some inner tepals with slightly swollen central veins. Achenes brown or dark brown, 0.9-1.2 × 0.6-0.8 mm. 2n = 8 (pistillate plants), 9 (staminate plants), 10 (both sexes). Flowering spring-summer. Dry to moist alluvial and ruderal habitats, river valleys, sandy plains, meadows, waste places; 0-500 m; Ala., Ark., Fla., Ga., Ill., Ind., Kans., La., Md., Miss., Mo., N.Y., N.C., Okla., Pa., S.C., Tenn., Tex., Va. Rumex hastatulus is distinct in subg. Acetosa and belongs to the monotypic subsect. Americanae Á. Löve & N. Sarkar. It is represented by at least two chromosome races: populations occurring from North Carolina to Florida and Mississippi normally have 2n = 8 in pistillate plants and 2n = 9 in staminate plants; populations from Louisiana to Texas and Oklahoma predominantly have 2n = 10 in both sexes. Rumex hastatulus has been reported from New Mexico (W. C. Martin and C. R. Hutchins 1980, vol. 1), but those records need confirmation. When fruiting, R. hastatulus has large inner tepals that distinguish it from R. acetosella, with which it is occasionally confused.
Dioecious perennial from a stout, woody root, 4-10 dm, branched from the base; basal lvs numerous, cauline lvs linear to hastately 3-lobed, the terminal lobe usually linear- oblong, the basal lobes commonly widely divergent, often unequal; infl 1-3 dm; staminate tep 1.5 mm, the outer obovate-oblong, the inner broadly obovate; outer tep of pistillate flowers reflexed in fr, barely 1 mm; valves broadly round-cordate, 2.5-3.5 mm, reticulate-veiny; achenes brown, 1.5 mm; 2n=26 (&), 27 (%). Sandy soil of the coastal plain; Mass. to Fla. and Tex., and n. in the Miss. Valley to Kans. and s. Ill.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.