Asclepias capricornu Woodson, Ann. Missouri Bot. Gard. 32: 370. 1945, based on Anantherix angustifolia Rafinesque, Atlantic J. 1: 146. 1832, not Asclepias angustifolia Schweigger 1812; Acerates decumbens (Nuttall) Decaisne; Anantherix decumbens Nuttall; Asclepias asperula var. decumbens (Nuttall) Shinners; Asclepiodora decumbens (Nuttall) A. Gray

Leaves blades lanceolate, 5–14.5 × 0.7–3.7 cm, apex acute to attenuate. Peduncles 0–6.8 cm. Corona segments white, reddish purple dorsally, 4.5–6 mm. Follicles 6–9(–11.5) cm, ribs sparsely to densely muricate for most of length. Seeds 5–7 × 4–5 mm.

Flowering Mar–Sep(–Nov); fruiting Apr–Sep(–Nov). Hills, slopes, ridge tops, plains, streambanks, dunes, pastures, fields, limestone, sandstone, gypsum, igneous substrates, rocky, clay, calcareous, and sandy soils, prairies, shrubby grasslands, oak-juniper, juniper, and oak woodlands; 50–1200 m; Kans., Nebr., Okla., Tex.

Subspecies capricornu is considered to be of conser­vation concern in Nebraska, where it has been recorded only at a single location in Nuckolls County.