Asclepias curassavica
Asclepias uncialis
blood flower, bloodflower milkweed, hierba de la cucaracha, tropical milkweed, wild ipecacuanha
dwarf milkweed, wheel milkweed
1–several, erect, sparsely to moderately branched, 30–150 cm, minutely pilosulous in a line to glabrate, not glaucous, rhizomes absent.
1–13, decumbent, unbranched or branched near base, 4–10 cm, puberulent with curved trichomes, not glaucous, rhizomatous.
persistent or gradually caducous from the base, opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole on a ciliate interpetiolar ridge;
petiole 4–25 mm, puberulent with curved trichomes in a line to glabrate;
blade elliptic or oval to linear, 4–18 × 0.3–4.5 cm, membranous, base cuneate, margins entire, apex acute to acuminate to attenuate, venation eucamptodromous to faintly brochidodromous, surfaces sparsely puberulent with curved trichomes on veins abaxially, sparsely puberulent with curved trichomes on veins to glabrate adaxially, margins 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, 5–22-flowered;
peduncle 0.5–8 cm, puberulent with curved trichomes in a line, with 1 caducous bract at the base of each pedicel.
terminal and extra-axillary at upper nodes, sessile, 3–7-flowered, bracts few.
7–20 mm, puberulent with curved trichomes.
10–18 mm, densely puberulent with curved trichomes.
erect;
calyx lobes linear-lanceolate, 3–4 mm, apex acute, puberulent with curved trichomes;
corolla red, sometimes yellow in throat (to wholly orange or yellow in cultivars), lobes reflexed with spreading tips, elliptic to oval, 6–9 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 2–2.5 mm;
fused anthers yellowish green to tan, cylindric, 1.5–2 mm, wings narrowly right-triangular, closed, apical appendages deltoid;
corona segments yellow to orange, stipitate, tubular, dorsally somewhat flattened, 3.5–4 mm, exceeding style apex, apex obtuse to acute, glabrous, internal appendage falcate, exserted, arching over style apex, glabrous;
style apex shallowly depressed, yellow.
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.
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose to smooth;
coma 2.5–3 cm.
broadly ovate, 7–8 × 5–6 mm, margin winged, erose, faces rugulose, lepidote;
coma 1.5–2 cm.
erect on straight pedicels, fusiform, 6–10 × 0.5–1.2 cm, apex acuminate to attenuate, smooth, glabrous.
erect on upcurved pedicels, ovoid, 3–5 × 0.8–1.5 cm, apex acuminate, smooth, minutely puberulent with curved trichomes.
= 22.
Asclepias curassavica
Asclepias uncialis
Asclepias curassavica is the only non-native Asclepias species naturalized in the flora area. It is very commonly cultivated, originally for its strikingly colored flowers and their attraction of Lepidoptera and Hymenoptera. Recently, they have been valued also as a host plant for monarch butterflies. Cultivars with pure orange or pure yellow flowers are readily available. The species develops rapidly from seed and can be grown as an annual (in the horticultural sense) anywhere in the region. Though often described as an annual, like all species of Asclepias, it has a perennial habit. It may persist through mild winters at least as far north as Oklahoma but has only become established in frost-free areas of the southern United States.
(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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