Asclepias brachystephana
Asclepias ruthiae
bract milkweed, short-crowned milkweed, shortcrown milkweed
Ruth's milkweed
4–25, erect, unbranched or branched near base, 20–40 cm, tomentulose, not glaucous, rhizomes absent.
1–8, decumbent, unbranched or branched near base, 9–10 cm, densely 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.
proximally opposite, distally alternate, petiolate, with 0 or 1 stipular colleter on either side of petiole;
petiole 2–5 mm, densely puberulent with curved trichomes;
blade ovate to lanceolate, 2–3 × 0.8–2 cm, chartaceous, base truncate to cuneate, margins entire, apex acute, venation eucamptodromous, surfaces persistently pilosulous, more densely so on veins, 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, 2–6-flowered, bracts few.
9–15 mm, tomentose.
15–25 mm, densely pilosulous to tomentulose.
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, pilose to tomentulose;
corolla red-violet, lobes reflexed with spreading tips, oval, 4–5 mm, apex acute, glabrous;
gynostegial column 0.2–0.5 mm;
fused anthers brown, cylindric, 1.5–2 mm, wings right-triangular, apical appendages ovate;
corona segments red-violet dorsally, white proximally, sessile, cupulate, 1.5–2 mm, slightly exceeded by style apex, apex truncate with a proximal tooth on each side, glabrous, internal appendage falcate, included in 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, 8–9 × 6–7 mm, margin corky-winged, erose, faces rugulose, minutely hirtellous;
coma 1–1.5 cm.
erect on upcurved pedicels, lance-ovoid, 5–7 × 1.2–1.8 cm, apex acuminate, shallowly ribbed, conspicuously striate, tomentulose.
erect to spreading on upcurved to spreading pedicels, ovoid, 3–3.5 × 0.7–1 cm, apex acuminate, smooth, pilosulous to tomentulose.
Asclepias brachystephana
Asclepias ruthiae
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.)
As discussed under Asclepias eastwoodiana, A. ruthiae is part of a complex of four species sometimes recognized as a single species. It is endemic to a small area in southeastern Utah (Emery, Sevier, and Wayne counties) on the periphery of the San Rafael Swell, the northeastern margin of Waterpocket Fold, and valleys north of the Henry Mountains. Reports from Arizona, New Mexico, and Monument Valley in Utah represent records of A. sanjuanensis. It commonly co-occurs with the similar A. macrosperma in this region and differs from the latter species by its more diminutive dimensions, red-violet corolla, and smaller, smooth fruit. Conservation status of this species requires re-assessment in light of the recent recognition of its more limited range.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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