Mead’s milkweed

Herbs. Stems 1 (rarely 2), erect, unbranched, 20–80 cm, gla­brous, glaucous, rhizomatous. Leaves opposite, sessile, with 1 stipular colleter on each side of petiole; blade ovate to lanceo­late, 4.5–10 × 1–5 cm, charta­ceous, base rounded to obtuse, margins entire, apex acute, ven­ation brochidodromous, surfaces glabrous, glaucous, margins inconspicuously ciliate, laminar colleters absent. Inflorescences terminal, rarely branched, pedun­culate, 7–19-flowered; peduncle (0–)3–10 cm, sparsely pilosulous to glabrate, glaucous, with 1 cadu­cous bract at the base of each pedicel. Pedicels 11–20 mm, pilo­sulous. Flowers pendent; calyx lobes narrowly lance­olate, 4–5 mm, apex acute, pilosulous; corolla green to greenish cream, sometimes tinged red, lobes reflexed with spreading tips, oval, 7–9 mm, apex acute, glabrous; gynostegial column 1.5–1.8 mm, fused anthers green, truncately obconic, 2–2.5 mm, wings right-triangular, closed, apical appendages ovate; corona segments green to yellowish green or greenish cream, sessile, con­duplicate, dorsally rounded, 4–5.5 mm, greatly exceed­ing style apex, base saccate, apex obtuse, emarginate, slightly flared, glabrous, internal appendage falcate, exserted, sharply inflexed towards style apex, glabrous; style apex shallowly depressed, green. Follicles erect on upcurved pedicels, narrowly fusiform, 7–14 × 0.9–1.6 cm, apex long-acuminate, smooth to minutely rugulose, puberulent with curved trichomes. Seeds ovate, 6–7 × 4–5 mm, winged, faces coarsely papillose; coma 3–4.5 cm.

Flowering May–Jun(–Jul); fruiting Jun–Aug. Dry, upland prairies, chert-lime glades; of conservation con­cern; 100–500 m; Ill., Ind., Iowa, Kans., Mo., Wis.

With respect to historical range reduction and poten­tial threats, Asclepias meadii is the most endangered North American milkweed species and is considered to be of conservation concern in each of the states in which it occurs. Nearly all of the viable populations are now restricted to Missouri and eastern Kansas; many of these are found in hay meadows, in which fruit maturation does not occur. Asclepias meadii is endemic to the highly-impacted tallgrass prairie ecoregion and is thought to be rare as a result of habitat loss. Consequently, concern for the continued existence of this species can be considered emblematic of concern for the tallgrass prairie as a whole. Active recovery efforts have achieved limited success, with newly established populations experiencing high mortality and slow growth of transplants. It has been re-introduced to Indiana and Wisconsin, but long-term survival of these populations is uncertain. The sessile, glaucous leaves and pendent umbels on a long peduncle suggest a diminutive version of A. elata; however, these species do not appear to be closely related (Fishbein et al. 2011). The terminal inflorescence of pendent umbels is unique among tallgrass prairie milkweeds.