Asclepias capricornu Woodson subsp. occidentalis Woodson

Leaves blades linear-lanceolate to linear, 7.7–17 × 0.4–3.6 cm, apex attenuate. Peduncles 0–22.5 cm. Corona segments red­dish purple with white upper margin, 5–7 mm. Follicles (6–)8–11.5 cm, ribs rarely inconspic­uously muricate near apex or not at all. Seeds 6–8 × 5–6 mm.

Flowering Mar–Sep(–Oct); fruiting (Apr–)May–Sep(–Oct). Slopes, hillsides, mesas, ridge tops, bajadas, canyons, arroyos, streamsides, lakesides, basalt, granite, limestone, shale, sandstone, alluvium, talus, rocky, gravelly, clay, sand, and silt soils, grasslands, pinyon-juniper, oak, juniper, pine, pine-oak, mixed conifer, and mesquite woodlands, chaparral, riparian areas, desert scrub; 700–2800 m; Ariz., Calif., Colo., Idaho, Nev., N.Mex., Okla., Tex., Utah; Mexico.

Although subsp. asperula is uncommon in Mexico, it ranges surprisingly far south, to Oaxaca. In the flora area, subsp. asperula has limited distributions in California (San Bernardino County), Idaho (Franklin County), Oklahoma (Cimarron County), and Texas (trans-Pecos region).