Michaux’s milkweed

Herbs. Stems 1–4 (rarely more), spreading to decumbent or ascending, unbranched, 15–30 cm, minutely puberulent with curved trichomes, not glaucous, rhizomes absent. Leaves opposite or alternate, sessile, often ascending and appearing secund, with 0 or 1 stipular colleter on each side of leaf base; blade narrowly linear, 4–9 × 0.1–0.4 cm, chartaceous, base cuneate, margins entire, apex acute, venation faintly eucamptodromous to obscure, surfaces glabrous, margins remotely ciliate to glabrate, laminar colleters absent. Inflorescences terminal, sometimes also extra-axillary at upper nodes, sessile or pedunculate, 6–28-flowered; peduncle 0–4 cm, minutely puberulent with curved trichomes, with 1 caducous bract at the base of each pedicel. Pedicels 9–12 mm, minutely puberulent on 1 side with curved trichomes. Flowers erect, calyx lobes narrowly lance­olate, 2.5–3 mm, apex acute, sparsely puberulent with curved trichomes to glabrate; corolla green to tan, tinged pink or red, inconspicuously striate, lobes reflexed with spreading tips, elliptic, 4–5 mm, apex acute, glabrous; gynostegial column 0.5–1 mm, fused anthers green, broadly cylindric, 1.5–3 mm, wings narrowly right-triangular, open at tip, apical appendages ovate; corona segments cream, often pink-striped, to magenta, stipi­tate, cupulate, margins not strongly incurved, 2.5–3.5 mm, slightly exceeding style apex, apex obtuse, glabrous, internal appendage falcate, exserted, sharply inflexed over style apex, glabrous; style apex shallowly depressed, pale to deep pink. Follicles erect on straight pedicels, narrowly fusiform, 7.5–12.5 × 0.5–0.7 cm, apex long-attenuate, smooth, minutely puberulent with curved trichomes. Seeds ovate, 7–8 × 5–6 mm, margin winged, faces smooth; coma 1.5–2.5 cm.

Flowering (Mar–)Apr–Jun(–Sep); fruiting May–Aug. Flats, hills, ridges, bogs, sandhills, ravines, ditches, clay, sandy, and silty soils, pine flatwoods, oak forests, savannas, wet prairies, often following fires; 0–200 m; Ala., Fla., Ga., La., Miss., S.C.

Asclepias michauxii occurs with, and bears an overall similarity to, A. longifolia. They are distinguished easily in flower by the cavitate corona segments with exserted appendages of A. michauxii. Commonly, A. michauxii has decumbent stems with secund leaves, unlike A. longifolia. In fruit, A. michauxii is distinguished easily by straight pedicels. Like A. longifolia, A. michauxii barely enters Louisiana, east of the Mississippi River (Livingston, Saint Tammany, and Tangipahoa parishes), and is considered to be of conservation concern in that state.