Asclepias curassavica
Asclepias prostrata
blood flower, bloodflower milkweed, hierba de la cucaracha, tropical milkweed, wild ipecacuanha
prostrate milkweed
1–several, erect, sparsely to moderately branched, 30–150 cm, minutely pilosulous in a line to glabrate, not glaucous, rhizomes absent.
2–7, prostrate to decumbent, sometimes branched, 15–30 cm, pilosulous to tomentulose, not glaucous, rhizomes absent.
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, petiolate, with 1 stipular colleter on either side of petiole;
petiole 2–3 mm, pilosulous to tomentulose;
blade linear-lanceolate to deltate, 1.8–5 × 0.4–1.8 cm, chartaceous, base truncate to rounded or subcordate, margins crisped, apex acute, mucronate, venation eucamptodromous, surfaces pilosulous to tomentulose, margins 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.
extra-axillary, pedunculate, 3–8-flowered;
peduncle 0.4–2 cm, densely pilosulous to tomentulose, with 1 caducous bract at the base of each pedicel.
7–20 mm, puberulent with curved trichomes.
8–14 mm, densely pilosulous to tomentulose.
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 lanceolate, 3–4 mm, apex acute, pilosulous;
corolla green, lobes reflexed, elliptic, 8–11 mm, apex acute, pilosulous abaxially, minutely hirtellous at base adaxially;
gynostegial column 3–3.5 mm;
fused anthers brown, obconic, 2–2.5 mm, wings right-triangular, closed, apical appendages ovate, erose;
corona segments cream, tinged dorsally yellow, green, or pinkish, subsessile, conduplicate-tubular, 5–7 mm, greatly exceeding style apex, apex truncate, glabrous, internal appendage falcate, exserted, sharply inflexed over style apex, papillose;
style apex shallowly depressed, green to yellowish.
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 corky-winged, erose, faces very sparsely papillose;
coma 1–1.8 cm.
erect on straight pedicels, fusiform, 6–10 × 0.5–1.2 cm, apex acuminate to attenuate, smooth, glabrous.
pendent on lax pedicels, ovoid, 3.5–5.5 × 1–1.5 cm, apex acuminate, muricate-ridged, tomentulose.
= 22.
Asclepias curassavica
Asclepias prostrata
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 prostrata is one of the most unusual and poorly known milkweeds in the flora. It was first collected by A. Schott in 1853 during the United States-Mexico border survey, along the Rio Grande (Río Bravo) between Laredo and Ringgold barracks (near Rio Grande City). However, it was not described until much later, from a collection made in Tamaulipas. The species remains rarely collected in both the United States and Mexico, and it is considered extremely rare in Texas (Starr and Zapata counties) and of conservation concern. Many historically known populations in the lower Rio Grande valley have not been relocated in recent years and are presumed extirpated (A. Strong, Texas Parks and Wildlife Department, pers. comm.). Several populations are known to have been eliminated by the widening of highways; others are thought to have been impacted by the spread of the invasive grass, Cenchrus ciliaris Linnaeus. The prostrate habit of A. prostrata cannot be confused with any other species of Asclepias. However, A. prostrata exhibits a remarkable similarity in all vegetative traits, including habit, to two co-occurring asclepiads, Matelea brevicoronata and M. parvifolia, as well as species of Acleisanthes (Nyctaginaceae), particularly the ubiquitous Acleisanthes longiflora. These species form a rather curious assemblage for which there is no hypothesized explanation involving convergent evolution. Since the description of Asclepias prostrata, prostrate species of Matelea occasionally have been misidentified as this species, even far outside its range.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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