Asclepias sullivantii
Asclepias linearis
asclépiade de Sullivant, prairie milkweed, Sullivant's milkweed
slim milkweed
solitary, erect, unbranched, 55–90 cm, glabrous, glaucous, rhizomatous.
1–4, erect, often branched, arrested vegetative branches absent, 30–75 cm, puberulent with curved trichomes in lines, 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, sessile, with 1 or 2 stipular colleters on each side of leaf base on a ciliate interpetiolar ridge;
blade linear, 3–8 × 0.1–0.3 cm, chartaceous, base cuneate, margins entire, apex acute, mucronate, venation obscure, surfaces glabrous abaxially, puberulent with curved trichomes adaxially, especially on midvein, to glabrate, margins 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.
extra-axillary at upper nodes, pedunculate, 7–20-flowered;
peduncle 1–1.5 cm, puberulent with curved trichomes on 1 side, with 1 caducous bract at the base of each pedicel.
22–36 mm, glabrous, glaucous.
6–8 mm, puberulent with curved trichomes on 1 side.
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 pendent;
calyx lobes linear-lanceolate, 1.5 mm, apex acute, pilosulous;
corolla green, tan, or pink, tinged red or brown, lobes reflexed with spreading tips, elliptic, 3–4 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1–1.2 mm;
fused anthers green, columnar, 1.2–1.5 mm, wings narrowly right-triangular, closed, apical appendages deltoid;
corona segments cream, stipitate, cupulate, dorsally flattened, 1.5 mm, exceeded by style apex, apex rounded, margin with a proximal tooth, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous;
style apex shallowly depressed, cream.
ovate, 7–9 × 5–6 mm, margin winged, faces minutely rugulose;
coma 3.5–4.5 cm.
ovate, 6–7 × 4–5 mm, margin winged, faces smooth;
coma 2–3 cm.
erect on upcurved pedicels, lance-ovoid, 7–11 × 1.5–3 cm, apex acuminate, sparsely muricate, sparsely pilosulous to glabrate, glaucous.
erect on straight pedicels, narrowly fusiform, 5–8.5 × 0.4–0.7 cm, apex acuminate to attenuate, smooth, sparsely pilosulous to glabrate.
= 22.
Asclepias sullivantii
Asclepias linearis
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.)
Although the range of Asclepias linearis is quite restricted, it is very common in grassland habitats on the coastal plain of southeastern Texas. Disjunct populations occur in the Dallas-Fort Worth area. It is similar in most respects to A. verticillata with the normally whorled leaves of that species the most reliable character distinguishing it from A. linearis. Although the ranges of these species overlap in the vicinity of Houston and Dallas-Fort Worth, and mixed populations have been reported, putative hybrids have not been documented, although they would be difficult to discern.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
IL Wildflowers
KS Wildflowers
MI Flora
MN Wildflowers
MO Plants
WildflowerSearch
iNaturalist
USDA Plants Database
