Swamp milkweed, asclépiade incarnate

Herbs. Stems 1–few, erect, unbranched to inflorescence, 30–150 cm, puberulent in a line with curved trichomes or densely pilose to glabrate, not glaucous, rhizomes absent. Leaves opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole on a ciliate inter­petiolar ridge; petiole 1–15 mm, pilosulous to pilose; blade lanceolate to linear-lanceolate or ovate, 5–15 × 0.5–4.5 cm, membranous, base obtuse to rounded or subcordate, margins entire, apex acute to acuminate or attenuate, venation eucamptodromous, surfaces sparsely puberulent with curved trichomes or pilose to glabrate, margins ciliate, 2–6 laminar colleters. Inflorescences extra-axillary at upper nodes, branched, pedunculate, 10–31-flowered; peduncle 1.5–7 cm, puberulent with curved trichomes to pilosulous, sometimes only on 1 side, to pilose, with 1 caducous bract at the base of each pedicel. Pedicels 10–15 mm, pilosulous to puberulent with curved trichomes, sometimes only on 1 side, to pilose. Flowers erect; calyx lobes lanceolate, 2–2.5 mm, apex acute, pilosulous to puberulent with curved trichomes; corolla pink to white, lobes reflexed with spreading tips, elliptic, (4.5–)5–6 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1.2–1.5 mm; fused anthers green to brown, columnar, 1.5–2 mm, wings narrowly right-triangular, slightly open at base, apical appendages deltoid; corona segments pink to white, often paler than corolla, stipitate, tubular, dorsally rounded to slightly flattened, 2–2.5 mm, ± equaling style apex, apex obtuse, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous; style apex shallowly depressed, green, white, or pink. Follicles erect on straight pedicels, fusiform, 6–9 × 0.8–1.2 cm, apex long-acuminate, smooth to indistinctly ribbed, sparsely puberulent with curved trichomes to pilose or pilosulous. Seeds ovate, 8–9 × 5–6 mm, margin broadly winged, faces smooth; coma 1.5–2 cm.

Subspecies 2 (2 in the flora): North America, n Mexico.

Asclepias incarnata can be grown in a great variety of soil types and is surprisingly drought tolerant consid­ering its natural predilection for hydric and mesic soils. As an easily grown, attractive, versatile species, it is one of the best options for gardening with milkweeds. It consists of two morphologically and geographically dis­tinct, but intergrading subspecies.

Lower Taxa

• Asclepias incarnata subsp. incarnata
• Asclepias incarnata subsp. pulchra (Ehrhart ex Willdenow) Woodson