Asclepias sullivantii
Asclepias purpurascens
asclépiade de Sullivant, prairie milkweed, Sullivant's milkweed
asclépiade pourpreé, purple milkweed
solitary, erect, unbranched, 55–90 cm, glabrous, glaucous, rhizomatous.
1, erect, unbranched, 50–120 cm, puberulent in lines with curved trichomes, not glaucous, rhizomatous.
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 (rarely whorled at 1 midstem node), petiolate, with 1 or 2 stipular colleters on each side of petiole, also in axil;
petiole 4–18 mm, puberulent with curved trichomes;
blade ovate or oval to lanceolate or elliptic, 6–20 × 2–10 cm, chartaceous, base cuneate, margins entire, apex obtuse to acute, apiculate, or mucronate, venation eucamptodromous to faintly brochidodromous, surfaces pilosulous, sparsely so adaxially, margins ciliate, 12–20 laminar colleters.
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, branched, also usually extra-axillary, sessile or pedunculate, 17–72-flowered;
peduncle 0–7 cm, puberulent with curved trichomes to pilosulous, with 1 caducous bract at the base of each pedicel.
22–36 mm, glabrous, glaucous.
12–28 mm, puberulent with curved trichomes.
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, 3–5 mm, apex acute, puberulent with curved trichomes;
corolla reddish purple, lobes reflexed with spreading tips, elliptic, 7–10 mm, apex acute, glabrous abaxially, papillose at base adaxially;
gynostegial column 1–1.5 mm;
fused anthers brown, cylindric, 2–2.5 mm, wings broadly right-triangular, closed to slightly open at tip, apical appendages ovate;
corona segments reddish purple, stipitate, conduplicate with a lateral flange on each side, 5–6 mm, greatly exceeding style apex, apex acute, glabrous, internal appendage falcate, exserted, sharply inflexed over style apex, glabrous;
style apex shallowly depressed, red-violet to green.
ovate, 7–9 × 5–6 mm, margin winged, faces minutely rugulose;
coma 3.5–4.5 cm.
ovate, 7–8 × 4–5 mm, margin winged, faces rugulose;
coma 3–4 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, lance-ovoid, 10–16 × 1.5–2.5 cm, apex long-acuminate, smooth, puberulent with curved trichomes.
= 22.
Asclepias sullivantii
Asclepias purpurascens
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 purpurascens is most common in rocky uplands of the Ozark Mountains and the piedmont of the northern Appalachian Mountains. Its reddish purple flowers are extremely showy and the species merits cultivation. The flowers have a strong cinnamon scent. Similarities to A. variegata and A. exaltata are discussed under those species. Although widespread in eastern North America, A. purpurascens is now rare over most of its range and has experienced a significant loss of populations and habitat everywhere but the Ozarks. It is considered to be of conservation concern in Connecticut, Delaware, Georgia (Floyd and Murray counties), Louisiana (Caldwell and Lincoln parishes), Maryland, Massachusetts, Michigan, Mississippi (Grenada and Washington counties), Nebraska (Nemaha and Richardson counties), New York, North Carolina, Tennessee, Virginia, and Ontario (Chatham-Kent, Essex, and Lambton counties). Moreover, it is presumed extirpated from the District of Columbia, Minnesota, New Hampshire, and Rhode Island. It has been reported, but not verified, from Maine and Vermont and, if historically present, is now extirpated there as well. Hybrids with A. amplexicaulis, A. exaltata, and A. syriaca have been documented from the New England and mid-Atlantic regions where A. purpurascens is now rare or extirpated. Putative hybrids exhibit intermediate floral and vegetative characteristics.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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