Asclepias brachystephana
Asclepias uncialis
bract milkweed, short-crowned milkweed, shortcrown milkweed
dwarf milkweed, wheel milkweed
4–25, erect, unbranched or branched near base, 20–40 cm, tomentulose, not glaucous, rhizomes absent.
1–13, decumbent, unbranched or branched near base, 4–10 cm, puberulent with curved trichomes, 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.
opposite and alternate, petiolate, with 1 stipular colleter on each side of petiole;
petiole 1–5 mm, puberulent with curved trichomes to pilosulous;
blade linear to lanceolate, 1.7–5 × 0.2–1 cm, chartaceous, base cuneate, margins entire, apex attenuate, venation obscure, surfaces puberulent on midvein with curved trichomes, margins densely ciliate, laminar colleters absent.
extra-axillary, pedunculate, 4–15-flowered;
peduncle 0.2–1.5 cm, tomentose, with 1 caducous bract at the base of each pedicel.
terminal and extra-axillary at upper nodes, sessile, 3–7-flowered, bracts few.
9–15 mm, tomentose.
10–18 mm, densely puberulent with curved trichomes.
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;
calyx lobes elliptic, 2–2.5 mm, apex acute, puberulent with curved trichomes;
corolla red-violet, lobes reflexed with spreading tips, oval, 3–5 mm, apex acute, glabrous;
gynostegial column 0.2–0.5 mm;
fused anthers brown, cylindric, 1–1.5 mm, wings narrowly right-triangular, apical appendages ovate, erose;
corona segments red-violet dorsally, white to orange proximally, sessile, cupulate, 1–2 mm, exceeded by style apex, apex truncate with a proximal tooth on each side, glabrous, internal appendage lingulate, barely exserted from cavity, glabrous;
style apex shallowly depressed, pink to red-violet.
oval to ovate, 6–7 × 4–6 mm, margin winged, faces papillate-tomentulose with dendritic scales;
coma 2–2.5 cm.
broadly ovate, 7–8 × 5–6 mm, margin winged, erose, faces rugulose, lepidote;
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.
erect on upcurved pedicels, ovoid, 3–5 × 0.8–1.5 cm, apex acuminate, smooth, minutely puberulent with curved trichomes.
Asclepias brachystephana
Asclepias uncialis
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 uncialis is by far the most widespread of the four diminutive, red-violet-petaled milkweeds of western North America (species 57–60). It typically has much narrower leaves than the other three species, and is extraordinarily cryptic in the absence of flowers in its characteristic short-grass prairie habitat, where its leaves closely mimic dominant grama grasses, particularly Bouteloua gracilis. Although it is widespread, it is encountered commonly only in southeastern Colorado and has only been recorded at single sites in Oklahoma (Cimarron County) and Texas (Andrews County), where the species should be considered to be of conservation concern. It is considered to be of concern in Colorado and New Mexico, but it is possible that this cryptic species is more common than has been recorded. Nonetheless, it appears that it has declined in northern Colorado. An 1873 specimen (C. C. Parry 246 [GH]) from Wyoming is the only documented record from that state and is from a highly disjunct location (attributed to Sweetwater County). It is possible that the reported location was in error; otherwise, it appears that A. uncialis has been extirpated from Wyoming, which is excluded from the range of the species in this treatment.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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