Asclepias curassavica
Asclepias elata
blood flower, bloodflower milkweed, hierba de la cucaracha, tropical milkweed, wild ipecacuanha
nodding milkweed
1–several, erect, sparsely to moderately branched, 30–150 cm, minutely pilosulous in a line to glabrate, not glaucous, rhizomes absent.
1 (rarely 2 or 3), erect, unbranched, 30–80 cm, glabrous, 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, sessile, with 1 inconspicuous stipular colleter on each side of leaf base;
blade oval or elliptic to oblong or lanceolate, 5.5–14 × 1.5–6 cm, subsucculent, base cordate, clasping, margins sometimes crisped, apex rounded to acute, mucronate, venation brochidodromous, surfaces glabrous, glaucous, margins minutely and remotely 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, pedunculate, 7–20-flowered;
peduncle 5–20 cm, pilosulous in a line, glaucous, with 1 caducous bract at the base of each pedicel.
7–20 mm, puberulent with curved trichomes.
20–32 mm, pilosulous, often in a line.
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.
pendent;
calyx lobes elliptic to oval, 5–8 mm, apex acuminate, sparsely pilosulous to glabrate;
corolla green, lobes reflexed with spreading tips, oval, 11–14 mm, apex acute, glabrous;
gynostegium sessile;
fused anthers green, obconic, 3–3.5 mm, wings narrowly right-triangular, thick, open just above base, apical appendages lanceolate;
corona segments white, yellow to tan dorsally, subsessile, conduplicate, 4–6 mm, equaling style apex, apex truncate, glabrous, internal appendage a crest, included in segment, glabrous;
style apex depressed, green to greenish cream.
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose to smooth;
coma 2.5–3 cm.
ovate to lanceolate, 6–7 × 3–6 mm, margin winged, sometimes minutely erose, faces rugulose;
coma 4–4.5 cm.
erect on straight pedicels, fusiform, 6–10 × 0.5–1.2 cm, apex acuminate to attenuate, smooth, glabrous.
erect on upcurved pedicels, fusiform to lance-ovoid, 8–13 × 1–2 cm, apex long-attenuate, smooth, pilosulous.
= 22.
Asclepias curassavica
Asclepias elata
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 elata is one of the few milkweeds in the flora area that possesses a mostly Mexican distribution but does not belong to the major clade that contains most of such species (species 23–27 here). Rather it is the sole representative in the flora, and the most northerly distributed member, of a small clade of glaucous, vegetatively homogeneous species ranging as far south as Costa Rica (M. Fishbein et al. 2011). Asclepias elata has been inconsistently recognized as distinct from A. glaucescens since the time of A. Gray et al. [1878–1897, vol. 2(1)]. However, at least since J. N. Rose (1892), the distinction between these species has been understood, and was presented clearly by R.E. Woodson Jr. (1954). Although indistinguishable in the absence of flowers, A. elata differs by fully pendent (versus erect to pendent) flowers, fewer flowers per umbel, longer corolla lobes, and corona segments that spread away from the gynostegium and are exceeded by the style apex, with the appendage merely a crest included in the segment (versus segments that are strict, overtop the style apex, and bear exserted appendages in A. glaucescens). Both species have extensive distributions, but they are largely allopatric, except in Mesoamerica. The northernmost populations of A. glaucescens are in Nayarit and San Luis Potosí. Asclepias elata is one of a cohort of species reaching their northwestern limits in Arizona that indicate biogeographic affinity of that region to the eastern slope of the Sierra Madre Occidental and Altiplano, rather than the western slope of the Sierra Madre Occidental. Other examples from the milkweed flora include A. brachystephana, A. involucrata, A. nummularia, A. oenotheroides, and A. quinquedentata. In Arizona, A. elata is known from Cochise, Graham, Pima, and Santa Cruz counties, in New Mexico from Eddy, Hidalgo, and Sierra counties, and in Texas from Brewster, Culberson, Jeff Davis, and Presidio counties.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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