Asclepias involucrata
Asclepias macrosperma
dwarf milkweed, largeseed milkweed
dwarf milkweed, large-seed milkweed, large-seed or dwarf or Eastwood's milkweed
1–15, decumbent, unbranched or branched near base, 5–18 cm, puberulent with curved trichomes to pilosulous, not glaucous, rhizomatous.
1–12, decumbent, unbranched or branched near base, 6–15 cm, densely puberulent with curved trichomes, not glaucous, rhizomatous.
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.
opposite or subopposite to alternate, petiolate, with 1 stipular colleter on either side of petiole;
petiole 1–5 mm, densely puberulent with curved trichomes;
blade lanceolate to linear-lanceolate or lance-ovate, 2.5–7 × 0.5–2 cm, chartaceous, base cuneate to truncate, margins crisped, apex attenuate, 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, sessile, 6–35-flowered, bracts few.
terminal, sessile, 12–40-flowered, bracts few.
12–19 mm, puberulent with curved trichomes to pilosulous.
9–19 mm, densely pilose.
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.
erect to pendent;
calyx lobes elliptic, 2.5–3 mm, apex acute, pilose;
corolla green, tinged red (especially abaxially), lobes reflexed, oval, 4–5.5 mm, apex acute, glabrous;
gynostegial column 0.2–0.8 mm;
fused anthers brown, cylindric, 1–1.5 mm, wings right-triangular, slightly open at tip, apical appendages ovate;
corona segments yellow to ochroleucous, subsessile, tubular, 2–3 mm, equaling or slightly exceeding style apex, apex truncate, glabrous, internal appendage falcate, exserted, sharply inflexed towards or over style apex, glabrous;
style apex shallowly depressed, green or pink.
ovate, 7–8 × 5–6 mm, margin thickly winged, faces papillose and rugulose, lepidote;
coma 1.5–2 cm.
ovate, 8–12 × 6–8 mm, margin thickly winged, faces densely rugulose;
coma 1.5–2 cm.
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.
erect on upcurved pedicels, ovoid, 5–6.5 × 1.2–2 cm, apex acuminate, rugose, faintly striate, densely pilosulous.
Asclepias involucrata
Asclepias macrosperma
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.)
Asclepias macrosperma has not been consistently recognized as distinct from A. involucrata, as discussed under that species. It is quite homogeneous across its range on the Colorado Plateau, and intermediates with A. involucrata only occur where the ranges contact on the southern and eastern margins of the Plateau. It is readily distinguished from typical A. involucrata by broader leaves with crisped margins and smaller corona segments that are less compressed, less flared apically, and nearly uniformly yellow, as opposed to cream with a dark dorsal stripe. Also, A. macrosperma is largely confined to sandy, often unstabilized substrates, whereas A. involucrata occurs on stable, rocky, clay to sandy soils across most of its range. Asclepias macrosperma has been documented at few sites in Colorado (Montezuma County) and New Mexico (San Juan County) and should be considered to be of conservation concern in these states. It appears secure in Utah and on Navajo lands in Arizona.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
KS Wildflowers
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