Asclepias curassavica
Asclepias hallii
blood flower, bloodflower milkweed, hierba de la cucaracha, tropical milkweed, wild ipecacuanha
Hall's milkweed
1–several, erect, sparsely to moderately branched, 30–150 cm, minutely pilosulous in a line to glabrate, not glaucous, rhizomes absent.
1–50, erect to ascending, unbranched or occasionally branched in inflorescence, 30–70 cm, puberulent with curved trichomes or pilose to glabrate, 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.
alternate to subopposite (sometimes congested into pseudo-whorls), petiolate, with 1–4 stipular colleters on each side of petiole;
petiole 10–20 mm, puberulent with curved trichomes to pilosulous;
blade narrowly lanceolate to ovate, 5–16 × 1.5–9 cm, chartaceous, base obtuse to truncate, often oblique or unequal, margins entire, apex acute to obtuse, mucronate, venation brochidodromous, surfaces pilosulous or tomentulose to glabrate, more densely so on veins, margins ciliate, 10–20 comparatively large laminar colleters.
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, sometimes branched, pedunculate, 9–29-flowered;
peduncle 0.5–10.5 cm, pilose to tomentulose, with 1 caducous bract at the base of each pedicel.
7–20 mm, puberulent with curved trichomes.
16–28 mm, densely pilose 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 to spreading;
calyx lobes lanceolate, 3–4 mm, apex acute, pilose;
corolla pale pink to red or green with pink or red tinge, lobes reflexed with spreading tips, lance-ovate, 7–8 mm, apex acute to obtuse, glabrous abaxially, minutely papillate at base adaxially;
gynostegial column 0.5–1 mm;
fused anthers brown, obconic, 2–2.5 mm, wings curved and widest at base to nearly right-triangular, closed, base distended, apical appendages ovate, erose;
corona segments cream with red or pink to purple dorsal stripe, sessile, conduplicate, dorsally flattened, 5–6.5 mm, greatly exceeding style apex, apex acute, glabrous, internal appendage falcate, exserted, sharply inflexed over style apex, glabrous;
style apex shallowly depressed, cream to pink.
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose to smooth;
coma 2.5–3 cm.
narrowly ovate, 6–7 × 4 mm, margin winged, faces and wings rugulose;
coma 2.5–3.5 cm.
erect on straight pedicels, fusiform, 6–10 × 0.5–1.2 cm, apex acuminate to attenuate, smooth, glabrous.
erect on upcurved pedicels, lance-ovoid, 8–12 × 0.7–1.5 cm, apex acuminate, smooth, pilosulous.
= 22.
Asclepias curassavica
Asclepias hallii
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 hallii is the only milkweed likely to be found above 2500 m in the Rocky Mountain and Intermountain regions, where it is found mostly on rocky canyon slopes. It appears to be a shorter-statured derivative of A. speciosa, which it greatly resembles, and which is the only species with which it commonly co-occurs. The range of A. hallii extends into the plains along river valleys and there overlaps with A. speciosa. Hybrids between these species have been documented only rarely in Colorado, and one of the syntypes of A. curvipes from Wyoming may represent this hybrid. Compared to A. speciosa, A. hallii is shorter statured, the leaves are narrower and are regularly subopposite or alternate rather than strictly opposite, and the corona segments are much shorter and erect. Despite overall similarities, it appears that these two species may not be close relatives (M. Fishbein et al. 2018).
The somewhat cruciform distribution of Asclepias hallii is odd and may be relictual. It extends from the eastern slope of the Rocky Mountains in Colorado west to the ranges of central Nevada, and from the Wasatch Range in northern Utah south to the Sierra Ancha in central Arizona. The species is fairly common at lower elevations of the Rocky Mountains in Colorado, particularly on the eastern slope, but is quite rare across the rest of its range, and it is considered to be of conservation concern in Utah. There are few documented occurrences in Arizona (Coconino, Gila, and Navajo counties), Nevada (Elko, Eureka, Lander, and White Pine counties), and New Mexico, where it has been documented by only a single specimen from Colfax County and may be extirpated. Its conservation status in these states merits evaluation. Asclepias hallii appears not to have been collected in Wyoming since 1958 and has been presumed to be extirpated; however, there is recent photo documentation from Albany County.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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