Asclepias brachystephana
Asclepias labriformis
bract milkweed, short-crowned milkweed, shortcrown milkweed
Utah milkweed, Utah or labriform or Jones' or poison milkweed
4–25, erect, unbranched or branched near base, 20–40 cm, tomentulose, not glaucous, rhizomes absent.
1–10, erect, unbranched (rarely distally), 15–70 cm, sparsely puberulent with curved trichomes to glabrate, not glaucous, rhizomatous.
opposite to subopposite, petiolate, with 1 or 2 stipular colleters on each side of petiole;
petiole 2–8 mm, tomentulose;
blade linear-lanceolate, 5–15 × 0.3–1.3 cm, chartaceous, base cuneate to rounded, margins often obscurely crisped, apex acute, mucronate, venation brochidodromous, surfaces tomentulose to glabrate, midvein puberulent with curved trichomes, margins minutely ciliate, laminar colleters absent.
alternate (subopposite), sessile or petiolate, with 1 or 2 stipular colleters on each side of petiole plus 4–8 in axil;
petiole 0–7 mm, glabrous;
blade linear-lanceolate to lanceolate, often falcate, 6–14.5 × 0.5–2 cm, chartaceous, base cuneate, margins entire, apex attenuate to acute, mucronate, venation brochidodromous (often faintly), surfaces glabrous, midvein sometimes sparsely puberulent with curved trichomes abaxially, margins eciliate, 0–12 laminar colleters.
extra-axillary, pedunculate, 4–15-flowered;
peduncle 0.2–1.5 cm, tomentose, with 1 caducous bract at the base of each pedicel.
extra-axillary, pedunculate, 6–28-flowered;
peduncle 0.2–2.5 cm, tomentose to glabrate, with 1 caducous bract at the base of each pedicel.
9–15 mm, tomentose.
15–25 mm, tomentose to glabrate.
erect;
calyx lobes ovate-lanceolate, 2–3 mm, apex acute, tomentulose;
corolla red-violet, sometimes green with red tinge, lobes reflexed, ovate, 4–6 mm, apex acute, minutely pilosulous;
gynostegium subsessile;
fused anthers brown, cylindric, 2–2.5 mm, wings right-triangular, closed, apical appendages ovate;
corona segments red-violet to pink basally, white apically, sessile, tubular, 1.5–2 mm, greatly exceeded by style apex, apex truncate, oblique, with a proximal tooth on each side, glabrous, internal appendage lingulate, slightly exserted, sharply inflexed towards gynostegium, glabrous;
style apex shallowly depressed, red-violet.
erect to pendent;
calyx lobes lanceolate, 3–4 mm, apex acute, sparsely pilose or tomentulose to glabrate;
corolla ochroleucous, lobes reflexed, tips sometimes spreading, oval to elliptic, 6–7 mm, apex acute, glabrous abaxially, minutely hirtellous at base adaxially;
gynostegial column 1–1.5 mm;
fused anthers green to yellowish green, obconic, 1.5–2 mm, wings narrowly right-triangular, tip distended, closed, apical appendages ovate;
corona segments ochroleucous to cream, substipitate, conduplicate, dorsally rounded, nearly tubular, 2.5–3.5 mm, slightly exceeding style apex, apex truncate with proximal tooth on each side, glabrous, internal appendage falcate, exserted, sharply inflexed over style apex, glabrous;
style apex shallowly depressed, cream or green.
oval to ovate, 6–7 × 4–6 mm, margin winged, faces papillate-tomentulose with dendritic scales;
coma 2–2.5 cm.
ovate to oval, 12–13 × 8–9 mm, margin winged, faces obscurely rugulose to smooth;
coma 1.5–2 cm.
erect on upcurved pedicels, lance-ovoid, 5–7 × 1.2–1.8 cm, apex acuminate, shallowly ribbed, conspicuously striate, tomentulose.
pendulous on spreading to pendulous pedicels, ovoid, 3.5–5.5 × 1.2–2 cm, apex acuminate, smooth, tomentulose to glabrate.
Asclepias brachystephana
Asclepias labriformis
Asclepias brachystephana is a blue-gray, bushy herb with ascending foliage, few-flowered umbels of small, red and white flowers, and conspicuously striped follicles. It is unlike any other milkweed. Nonetheless, herbarium specimens are commonly confused with those of A. asperula because the herbage of A. brachystephana turns green on drying, and the leaves of A. asperula subsp. asperula are often of similar size and shape. However, leaf arrangement in A. asperula is alternate rather than opposite. The flowers of A. brachystephana are remarkably similar to, and convergent with, those of A. cutleri, A. eastwoodiana, A. ruthiae, A. sanjuanensis, and A. uncialis (M. Fishbein et al. 2011). In Arizona, A. brachystephana is restricted to the portion of the southeastern corner of the state with Chihuahuan floristic affinities, in Cochise, Graham, Pima, and Santa Cruz counties.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asclepias labriformis is endemic to Utah (Emery, Garfield, Grand, Uintah, and Wayne counties) and is found in a remarkably narrow northeast–southwest band from the terraces surrounding the San Rafael Swell west of Green River, across Waterpocket Fold, to arroyo beds below the Kaiparowits Plateau southeast of Escalante. It shares pendulous follicles with several other milkweed species inhabiting sandy habitats, such as its close relative A. welshii, and more distant relatives A. cutleri and A. subulata. Asclepias labriformis is reputed to be one of the milkweeds that is most poisonous to livestock (J. M. Benson et al. 1979).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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