Asclepias meadii
Asclepias involucrata
Mead's milkweed
dwarf milkweed, largeseed milkweed
1 (rarely 2), erect, unbranched, 20–80 cm, glabrous, glaucous, rhizomatous.
1–15, decumbent, unbranched or branched near base, 5–18 cm, puberulent with curved trichomes to pilosulous, not glaucous, rhizomatous.
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.
opposite or subopposite to alternate, petiolate, with 1 or 2 stipular colleters on either side of petiole;
petiole 1–2 mm, pilosulous to glabrate;
blade linear to narrowly lanceolate, 1.5–12 × 0.2–0.8 cm, chartaceous, base cuneate to truncate, margins sometimes crisped, apex acute, mucronate, venation obscure to faintly eucamptodromous, surfaces sparsely pilosulous to glabrate, midvein puberulent with curved trichomes to pilosulous, margins densely ciliate, laminar colleters absent.
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.
terminal, sessile, 6–35-flowered, bracts few.
11–20 mm, pilosulous.
12–19 mm, puberulent with curved trichomes to pilosulous.
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.
erect to spreading;
calyx lobes elliptic, 2.5–3 mm, apex acute, pilosulous;
corolla green, sometimes tinged pink or red (especially abaxially), lobes reflexed, elliptic, 4.5–6 mm, apex acute, glabrous;
gynostegial column 0.5–1 mm;
fused anthers brown, cylindric, 1.5–2 mm, wings right-triangular, slightly open at tip, apical appendages ovate;
corona segments cream, usually with a pink or red dorsal stripe, subsessile, conduplicate, 3.5–4.5 mm, slightly exceeding style apex, apex truncate with a spreading tip, glabrous, internal appendage falcate, exserted, sharply inflexed towards the style apex, glabrous;
style apex shallowly depressed, cream or greenish cream to pink.
ovate, 6–7 × 4–5 mm, winged, faces coarsely papillose;
coma 3–4.5 cm.
ovate, 7–8 × 5–6 mm, margin thickly winged, faces papillose and rugulose, lepidote;
coma 1.5–2 cm.
erect on upcurved pedicels, narrowly fusiform, 7–14 × 0.9–1.6 cm, apex long-acuminate, smooth to minutely rugulose, puberulent with curved trichomes.
erect on upcurved pedicels, ovoid, 4.5–5.5 × 1.5–2 cm, apex acuminate, rugose, faintly striate, minutely puberulent with curved trichomes to pilosulous.
Asclepias meadii
Asclepias involucrata
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Despite the common name dwarf milkweed, Asclepias involucrata is larger than the sympatric A. uncialis, to which it bears a great similarity in the absence of flowers or fruit. In such conditions, A. involucrata is highly cryptic among the short-statured bunch grasses with which it grows. It senesces typically by summer’s end, contributing to the impression that the species is not common. It has occasionally been circumscribed to include A. macrosperma (for example, E. Sundell 1994), although the distinctions made by R. E. Woodson Jr. (1954) were sound. Nonetheless, where the ranges of these largely parapatric species meet, in an arc from northwestern New Mexico to central Arizona, plants of intermediate morphology can be found. It is unknown whether these represent relics of the speciation process or examples of recent hybridization. Asclepias involucrata is rare and of conservation concern in Colorado (Baca, Bent, and Las Animas counties) and Oklahoma (Cimarron County). It is probably extirpated from Kansas (Stevens County), where it is known from a single, historical record. Reports from northern Arizona, southwestern Colorado, and Utah are based on records of A. macrosperma.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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