Wooly or sidecluster or small-green milkweed, asclépiade laineuse

Herbs. Stems 1 or 2 (rarely more), erect to spreading, unbranched, 7–20 cm, densely hirtellous to pilose, not glau­cous, rhizomatous. Leaves oppo­site or alternate, petiolate, with 1 stipular colleter on each side of petiole; petiole 1–2 mm, hirtellous; blade oblong or lan­ceolate to narrowly lanceolate, 4–8 × 0.5–2.7 cm, chart­aceous, base cuneate to rounded or subcordate, margins entire, apex acute to obtuse, venation eucamptodromous to reticulodromous, surfaces hirtellous, margins ciliate, laminar colleters absent. Inflorescences terminal, usually solitary, pedunculate, 17–50-flowered (rarely more); peduncle 1–3 cm, densely hirtellous to pilose, with 1 caducous bract at the base of each pedicel. Pedicels 9–13 mm, hirtellous to pilose. Flowers erect to spread­ing; calyx lobes narrowly lanceolate, 1.5–2 mm, apex acute, hirtellous; corolla greenish cream, sometimes purple-tinged, lobes reflexed, oblong, 3–5 mm, apex acute, glabrous; gynostegial column 0–0.2 mm; fused anthers green, broadly cylindric, 1.5–2 mm, wings tri­angular, widest below middle, closed, apical appendages ovate; corona segments cream to greenish cream, sessile, chute-shaped, margins incurved, appressed to column, 2–3.5 mm, exceeded by style apex, base saccate, apex rounded, glabrous, internal appendage absent or obscure, glabrous; style apex shallowly depressed, green to greenish cream. Follicles erect on upcurved pedicels, fusiform, 8–10 × 0.8–1.5 cm, apex long-acuminate, smooth, hirtellous to pilose. Seeds ovate, 6–7 × 4–5 mm, faces minutely rugulose; comose. 2n = 22.

Flowering May–Aug; fruiting Jul–Aug. Sandhills, dunes, moraines, bluffs, slopes, sandstone, limestone, sandy, gravel, or rocky soils, prairies, pine barrens and forests, oak savannas; 200–700 m; Man.; Ill., Iowa, Kans., Minn., Nebr., N.Dak., S.Dak., Wis.

Asclepias lanuginosa is highly cryptic due to its small stature and early flowering. It resembles a short, hirtellous form of A. viridiflora. In addition to the differences in vestiture, A. lanuginosa can be distinguished from that species by the terminal inflorescence and the cream-colored corona segments. Due to severe habitat loss in the tallgrass prairie region, A. lanuginosa has apparently declined and is of conservation concern over much of its range, that is, in Illinois, Iowa, Kansas, North Dakota, South Dakota, and Wisconsin. It is more secure in Nebraska, but an overall re-assessment of the status of this species is warranted. The only report from Montana is from the “Yellowstone expedition,” which may not have been collected in the state. R. E. Woodson Jr. (1954) considered A. lanuginosa Kunth (a later homonym) to be the correct name for a Mexican species, A. otarioides E. Fournier. He soon realized that A. lanuginosa Nuttall has priority, but prior usage and his extensive annotations produced lingering confusion over the correct name of the Mexican species. Torrey’s replacement name for this species, A. nuttalliana, is illegitimate, as it was superfluous on publication.