Asclepias obovata
Asclepias uncialis
pineland milkweed
dwarf milkweed, wheel milkweed
1 (rarely more), erect to spreading, unbranched, 40–70(–200) cm, densely hirtellous to velutinous, not glaucous, rhizomes absent.
1–13, decumbent, unbranched or branched near base, 4–10 cm, puberulent with curved trichomes, not glaucous, rhizomatous.
opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole;
petiole 1–4 mm, densely hirtellous to velutinous;
blade oblong or elliptic to obovate or ovate, 4–9 × 1–3.5 cm, subcoriaceous, base rounded or truncate to cordate, margins sometimes crisped, apex acute to truncate, sometimes emarginate, often mucronate, venation brochidodromous, surfaces densely hirtellous to velutinous abaxially, hirtellous adaxially, margins ciliate, 8–12 laminar colleters.
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, sometimes also appearing terminal, sessile or pedunculate, 7–31-flowered;
peduncle 0–0.5 cm, densely hirtellous to velutinous, with 1 caducous bract at the base of each pedicel.
terminal and extra-axillary at upper nodes, sessile, 3–7-flowered, bracts few.
10–12 mm, densely hirtellous to velutinous.
10–18 mm, densely puberulent with curved trichomes.
erect to pendent;
calyx lobes elliptic, 5–6 mm, apex acute, densely hirtellous;
corolla green, sometimes tinged reddish or bronze, lobes reflexed, sometimes with spreading tips, elliptic, 7–9 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1–1.5 mm;
fused anthers green, obconic, 2.5–4 mm, wings right-triangular, open at base, apical appendages broadly ovate;
corona segments bronze to yellow, often tinged red, sometimes apically cream or pale, stipitate, tubular, somewhat flattened laterally, flared at base, 5–8 mm, greatly exceeding style apex, apex rounded, flared, glabrous, internal appendage falcate, exserted, sharply incurved over style apex, glabrous;
style apex shallowly depressed, green.
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.
broadly ovate, 8–9 × 6–7 mm, margin winged, faces smooth;
coma 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, narrowly to broadly fusiform, 7.5–12.5 × 1.5–2.5 cm, apex acuminate, smooth, densely hirtellous to velutinous.
erect on upcurved pedicels, ovoid, 3–5 × 0.8–1.5 cm, apex acuminate, smooth, minutely puberulent with curved trichomes.
Asclepias obovata
Asclepias uncialis
Asclepias obovata is a common milkweed of seasonally wet, sandy soils in pine woodlands of the Gulf Coastal Plain and (rarely) the southern Atlantic Coastal Plain. It is rare and considered to be of conservation concern in Arkansas.
(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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