Asclepias perennis

Subshrubs or herbs, cespitose. Stems 1–5, erect, sparsely to moderately branched, especially towards base, 30–60 cm, puber­ulent with curved trichomes in a line to glabrate, not glaucous, rhizomatous. Leaves persistent or gradually caducous from the base, opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole on a ciliate interpetiolar ridge; petiole 10–12 mm, ciliate; blade nar­rowly elliptic to oval or oblong, 5–14 × 0.3–3 cm, mem­branous or chartaceous, base cuneate, margins entire, apex acute to attenuate or acuminate, minutely mucro­nate, venation faintly brochidodromous to eucamp­todromous, surfaces sparsely puberulent with curved tri­chomes, more densely on veins, to glabrate, margins inconspicuously ciliate, laminar colleters absent. Inflorescences extra-axillary at upper nodes, sometimes appearing terminal, pedunculate, 12–30-flowered; peduncle 1.5–5 cm, puberulent with curved trichomes, sometimes only on 1 side, with 1 caducous bract at the base of each pedicel. Pedicels 7–13 mm, puberulent with curved trichomes, sometimes only on 1 side. Flowers erect to spreading; calyx lobes narrowly lance­olate to linear, 1.2–1.5 mm, apex acute, puberulent with curved trichomes; corolla white to pink-tinged, lobes reflexed with spreading tips, elliptic, 3–4 mm, apex acute to obtuse, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 0.8–1.2 mm; fused anthers brown, cylindric, 1.5–2 mm, wings narrowly right-triangular, closed, apical appendages deltoid; corona segments white, sometimes faintly pink-tinged, stipitate, tubular, dorsally rounded, 1.5–2.5 mm, slightly exceeding style apex, apex obtuse to acute, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous; style apex shallowly depressed, white, sometimes pink-tinged. Follicles pendulous on declined pedicels, lance-ovoid, 4–7 × 1–2.5 cm, apex long-acuminate, smooth, glabrous. Seeds broadly oval, 12–15 × 11–14 mm, margin broadly winged, faces smooth; coma absent.

Phenology: Flowering (Mar–)Apr–Nov; fruiting Jun–Dec.
Habitat: Swamps, streamsides, ditches, bottomlands, flood plains, marshes, saturated or inundated clay, silty, and sandy soils, pine-oak, oak, and mixed hardwood for­ests, riparian woods, pine flatwoods.
Elevation: 0–300(–500?) m.

Distribution

• Generated Map
• Legacy Map

Ala., Ark., Fla., Ga., Ill., Ind., Ky., La., Miss., Mo., S.C., Tenn., Tex.

Discussion

Asclepias perennis is the most hydrophytic North American milkweed and is often found emerging from standing water in swamps and ditches. The pendulous fruits and hairless seeds are distinctive; it is the only milkweed in the United States with seeds lacking a coma, and only one of three such species in North America. It is widely distributed along the coastal plain; inland (Arkansas, Illinois, Indiana, Kentucky, Missouri, Tennessee), it is restricted to the valleys of the Mississippi and Ohio rivers and their tributaries.

Selected References

None.

Lower Taxa

None.