Asclepias curassavica
Asclepias engelmanniana
blood flower, bloodflower milkweed, hierba de la cucaracha, tropical milkweed, wild ipecacuanha
Engelmann's milkweed
1–several, erect, sparsely to moderately branched, 30–150 cm, minutely pilosulous in a line to glabrate, not glaucous, rhizomes absent.
1 or 2 (rarely more), erect, sometimes branched, 40–160 cm, glabrous, 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.
alternate, sessile, drooping, with 1 stipular colleter on each side of leaf base;
blade linear, conduplicate, 5–19 × 0.15–0.3 cm, chartaceous, base cuneate, margins entire, apex acute, venation faintly brochidodromous to obscure, surfaces sparsely puberulent with curved trichomes to glabrate, 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, sessile or pedunculate, 14–23-flowered;
peduncle occasionally branched, 0–2 cm, pilosulous or puberulent with curved trichomes, with 1 caducous bract at the base of each pedicel.
7–20 mm, puberulent with curved trichomes.
8–11 mm, pilose.
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, pilosulous;
corollas tan to russet abaxially, pale green to greenish cream or ochroleucous to tan adaxially, lobes reflexed with ascending tips, elliptic, 4–5 mm, apex acute, glabrous;
gynostegial column 0.5–1.5 mm;
fused anthers brown, broadly barrel-shaped, 2–2.5 mm, wings crescent-shaped and narrowly open throughout, apical appendages narrowly pandurate, conduplicate, not obscuring corpuscula;
corona segments cream to tan or yellow, sessile, chute-shaped, 2–3 mm, equaling style apex, base saccate and auriculate, apex retuse to nearly truncate, glabrous, internal appendage absent or obscure, glabrous;
style apex depressed, green to yellowish green.
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose to smooth;
coma 2.5–3 cm.
ovate, 8–9 × 5–6 mm, margin winged, faces minutely papillose and rugulose;
coma 2–2.5 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, 6–10 × 1.2–2 cm, apex long-acuminate, smooth, pilosulous.
= 22.
Asclepias curassavica
Asclepias engelmanniana
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 engelmanniana is usually a tall herb with drooping leaves and spherical umbels of greenish yellow flowers rising above surrounding grassland plants. In spite of its distinctive appearance, it is quite similar to its close relatives, A. rusbyi and A. stenophylla. The yellowish green coronas, squat flowers, upcurved fruiting pedicels, and drooping leaves distinguish A. engelmanniana from A. stenophylla, which has more slender flowers with creamy coronas, straight pedicels in fruit, and spreading to ascending leaves. Despite ranges with only little overlap and few if any mixed populations, these two species are often confused, especially in the absence of flowers. Compared to its close relative, A. engelmanniana is distributed further west, in mixed- and short-grass prairies. A report of A. engelmanniana from South Dakota has not been confirmed, and reports from Iowa appear to have been based on misidentified specimens of A. stenophylla. Reports from Arkansas are unconfirmed and also very likely to be based on misidentifications. Asclepias engelmanniana is considered to be of conservation concern in Wyoming, where it has been recorded only from Goshen County. Asclepias rusbyi has been inconsistently distinguished from A. engelmanniana (for example, E. Sundell 1994), although the differences elucidated by R. E. Woodson Jr. (1954) are sound. These species are readily distinguished by the characters in the key and appear to have allopatric ranges. Reports of A. engelmanniana from Arizona, western New Mexico, Nevada, Utah, southwestern Colorado, and Sonora, Mexico, all pertain to A. rusbyi.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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