Asclepias sullivantii
Asclepias solanoana
asclépiade de Sullivant, prairie milkweed, Sullivant's milkweed
prostrate milkweed, serpentine milkweed
solitary, erect, unbranched, 55–90 cm, glabrous, glaucous, rhizomatous.
1–15, prostrate, unbranched (rarely branched), 15–40 cm, densely puberulent with curved trichomes to tomentose, not glaucous, rhizomes absent.
opposite, sessile, with 1 or 2 stipular colleters on each side of leaf base;
blade lanceolate or ovate to oblong, 6.5–15 × 1.5–9 cm, succulent, base cordate, margins entire, apex obtuse to rounded or acute, sometimes emarginate, mucronate, venation brochidodromous, surfaces glabrous, glaucous, margins eciliate, 4–12 laminar colleters.
opposite, petiolate, stipular colleters absent;
petiole 5–10 mm, densely puberulent with curved trichomes;
blade ovate to nearly orbiculate, 3.5–6 × 3–4 cm, subsucculent, base obtuse to cordate, margins entire, apex obtuse to acute or rounded, venation eucamptodromous, surfaces pilosulous, more densely so abaxially, especially on veins, becoming glabrate adaxially, margins inconspicuously ciliate, laminar colleters absent.
extra-axillary at upper nodes, sometimes appearing terminal, pedunculate, 9–29-flowered;
peduncle 1–6 cm, glabrous, glaucous, with 1 caducous bract at the base of each pedicel.
terminal and extra-axillary, pedunculate, 20–55-flowered;
peduncle 1.5–9 cm, tomentose, with 1 caducous bract at the base of each pedicel.
22–36 mm, glabrous, glaucous.
10–13 mm, tomentose to pilose.
erect;
calyx lobes lanceolate, 4–5 mm, apex acute, glabrous, glaucous;
corolla dark pink, pale at base of lobes, lobes reflexed, sometimes with spreading tips, elliptic, 8–12 mm, apex acute, glabrous;
gynostegial column 1–1.5 mm;
fused anthers truncately green, obconic, 2.5–3.5 mm, wings narrowly right-triangular, open at base, apical appendages ovate;
corona segments pale to dark pink, subsessile, tubular, flattened dorsally, 5–7 mm, exceeding style apex, apex broadly obtuse, oblique, glabrous, internal appendage subulate, exserted, sharply inflexed over style apex, glabrous;
style apex shallowly depressed, green.
erect to spreading;
calyx lobes lanceolate, 2–3 mm, apex acute, pilose to tomentose;
corolla pale pink to red, lobes reflexed with spreading tips, oval, 5–6 mm, apex acute, glabrous;
gynostegium sessile;
fused anthers yellow to brown or green, broadly barrel-shaped, 1.5–2 mm, wings deltoid, widest at middle, closed, apical appendages ovate;
corona segments pinkish cream to cream, subsessile, conduplicate, dorsally rounded, spreading away from anthers, 2–3 mm, greatly exceeded by style apex, apex truncate, glabrous, internal appendage absent;
style apex shallowly depressed, cream to green.
ovate, 7–9 × 5–6 mm, margin winged, faces minutely rugulose;
coma 3.5–4.5 cm.
ovate, 6–8 × 5–6 mm, margin very narrowly winged, faces rugulose;
coma 2–2.5 cm.
erect on upcurved pedicels, lance-ovoid, 7–11 × 1.5–3 cm, apex acuminate, sparsely muricate, sparsely pilosulous to glabrate, glaucous.
erect on upcurved pedicels (at least until maturity), lance-ovoid, 6–10 × 2–3 cm, apex obtuse to acuminate, longitudinally ridged, pilosulose or tomentulose to glabrate.
= 22.
Asclepias sullivantii
Asclepias solanoana
The distribution of Asclepias sullivantii is coextensive with the tallgrass prairie, where it favors moist sites. The broad, smooth, glaucous, clasping leaves, often with pink venation, are similar only to A. amplexicaulis in the region, but the latter species favors dry sites and has a long, terminal peduncle. Because of the tremendous reduction in the extent and quality of tallgrass prairie, A. sullivantii is presumed to be less common than in former times and is considered to be rare and of conservation concern in Michigan, Minnesota, Wisconsin, and Ontario (Chatham-Kent, Elgin, Essex, Lambton, and Middlesex counties). It may be extirpated from North Dakota (historically in Cass and Richland counties) and South Dakota (historically in Clay, Lincoln, and Union counties). In Nebraska, it is limited to the eastern one-third of the state. Nonetheless, it is encountered commonly in suitable habitat along roadsides in the core of its range, in Illinois and Kansas. Asclepias sullivantii commonly co-occurs with and is often mistaken for A. syriaca from a distance but is easily distinguished by its smaller stature, ascending leaves, and the concentration of umbels at the apex of the stem, in addition to the glabrous and glaucous herbage that can be observed with closer examination. It is known to hybridize rarely with A. syriaca, and presumed hybrids can be recognized by intermediate vegetative and floral features.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asclepias solanoana is a delightful and unique milkweed that is endemic to rugged, serpentine barrens in the northern Coast Range of California. The plants hug the ground, the stems seeming to crawl outward propelled by the highly unusual metallic, grayish or bluish green, ovate leaves. Bright pinkish rose balls of floral buds are held above, and are followed by variegated spheres of cream, pink, green, and brown flowers with a vague resemblance to heads of Abronia (Nyctaginaceae). It is often the only conspicuous plant species on highly exposed, south-facing slopes. S. P. Lynch (1977) documented Hymenoptera (carpenter bees, Xylocopa, bumblebees, Bombus, and honeybees, Apis) to be the main pollinators of A. solanoana. It is considered threatened by extractive industries and recreation at some sites. A naturally occurring population has been reported from southern Oregon and needs confirmation.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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