10. Euphorbia hexagona Nuttall ex Sprengel, Syst. Veg. 3: 791. 1826.
Six-angle spurge Six-angle spurge
Herbs, annual, with taproot. Stems erect, unbranched or branched, 30–70(–100) cm, sparsely hispid, occasionally densely so at distal nodes. Leaves opposite; stipules (0–)0.1 mm; petiole 1–4 mm, pilose; blade linear-filiform, linear, or elliptic, 21–40 × 0.9–7.5 mm, base attenuate, margins entire, apex acute, abaxial surface sparsely hispidulous to strigillose, adaxial surface glabrous; venation obscure, only midvein conspicuous. Cyathia solitary in leaf axils or in terminal cymes or dichasia; peduncle 1–2.1 mm, strigillose. Involucre campanulate, 1–1.5 × (1–)1.5–1.8 mm, hispid; glands 5, green to deep red, elliptic to reniform, 0.5 × 0.8–1 mm; appendages white to green, tinged red, deltate to ovate, 0.7–1.7 × (0.9–)1.3–1.5 mm, entire. Staminate flowers 15–30(–40). Pistillate flowers: ovary glabrous; styles 0.7–1.1 mm, 2-fid nearly entire length. Capsules subglobose to broadly ovoid, 4.7–6.5 × 4.9–6.5(–7.1) mm, glabrous; columella 3.5–4.5 mm. Seeds dark brown or dark gray, ovoid, 3.4 × 2.7 mm, rugose, whitish glaucous; caruncle absent.
Flowering and fruiting late summer–fall. Sand prairies, other sandy soil habitats, stream banks, sand bars, damp places; 200–1300 m; Ark., Colo., Ill., Iowa, Kans., Minn., Mo., Mont., Nebr., N.Mex., Okla., S.Dak., Tex., Wis., Wyo.
Euphorbia hexagona is native to the central United States and is most common from southern South Dakota to Oklahoma and northern Texas.