in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 186. 1859.
Herbs, perennial, with moderately to strongly thickened rootstock. Stems prostrate to decumbent, mat-forming, 5–30 cm, appressed wooly, strigillose, or short-sericeous. Leaves opposite; stipules distinct, subulate, 0.2–0.5 mm, appressed wooly to sericeous; petiole 0.3–0.8 mm, appressed wooly to sericeous; blade ovate to elliptic, 1.5–5.5 × 1.3–4 mm, base asymmetric, obtuse to hemicordate, margins entire often reddish, apex usually obtuse, occasionally acute (young leaves), surfaces sericeous to strigillose or slightly pilose, adaxial surface often glabrous; 3-veined from base but only midvein conspicuous. Cyathia solitary at distal nodes; peduncle 0.2–0.3 mm. Involucre turbinate, 0.8–1.3 × 1.2–2 mm, appressed wooly, sericeous, or strigillose; glands 4, purple-black, elliptic to oblong, 0.2–0.3 × 0.4–0.6 mm; appendages absent or reddish pink, forming narrow rim around distal margin of gland, 0–0.1 × 0–0.6 mm, distal margin entire, crenulate, or erose. Staminate flowers 15–20. Pistillate flowers: ovary canescent; styles 0.3–0.5 mm, 2-fid at apex. Capsules subglobose to broadly ovoid, 1.3–1.7 × 1.5–1.8 mm, canescent; columella 1–1.3 mm. Seeds white to pinkish or light brown, ovoid, 4-angled in cross section, 1–1.4 × 0.6–0.8 mm, smooth to rugulose or rarely with 1–2 inconspicuous transverse ridges. 2n = 32.
Phenology: Flowering and fruiting year-round (mostly spring–fall).
Habitat: Desert scrub, oak and juniper woodlands, thorn scrub, shrublands, grasslands, frequently on limestone substrates.
Elevation: 70–1400 m.
In the flora area, Euphorbia cinerascens is found only in southern and western Texas. In Mexico, it is found from Chihuahua east to Tamaulipas, south to Guanajuato.