Asclepias obovata
Asclepias linearis
pineland milkweed
slim milkweed
1 (rarely more), erect to spreading, unbranched, 40–70(–200) cm, densely hirtellous to velutinous, not glaucous, rhizomes absent.
1–4, erect, often branched, arrested vegetative branches absent, 30–75 cm, puberulent with curved trichomes in lines, not glaucous, rhizomatous.
opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole;
petiole 1–4 mm, densely hirtellous to velutinous;
blade oblong or elliptic to obovate or ovate, 4–9 × 1–3.5 cm, subcoriaceous, base rounded or truncate to cordate, margins sometimes crisped, apex acute to truncate, sometimes emarginate, often mucronate, venation brochidodromous, surfaces densely hirtellous to velutinous abaxially, hirtellous adaxially, margins ciliate, 8–12 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, sometimes also appearing terminal, sessile or pedunculate, 7–31-flowered;
peduncle 0–0.5 cm, densely hirtellous to velutinous, 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.
10–12 mm, densely hirtellous to velutinous.
6–8 mm, puberulent with curved trichomes on 1 side.
erect to pendent;
calyx lobes elliptic, 5–6 mm, apex acute, densely hirtellous;
corolla green, sometimes tinged reddish or bronze, lobes reflexed, sometimes with spreading tips, elliptic, 7–9 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1–1.5 mm;
fused anthers green, obconic, 2.5–4 mm, wings right-triangular, open at base, apical appendages broadly ovate;
corona segments bronze to yellow, often tinged red, sometimes apically cream or pale, stipitate, tubular, somewhat flattened laterally, flared at base, 5–8 mm, greatly exceeding style apex, apex rounded, flared, glabrous, internal appendage falcate, exserted, sharply incurved 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.
broadly ovate, 8–9 × 6–7 mm, margin winged, faces smooth;
coma 2–5 cm.
ovate, 6–7 × 4–5 mm, margin winged, faces smooth;
coma 2–3 cm.
erect on upcurved pedicels, narrowly to broadly fusiform, 7.5–12.5 × 1.5–2.5 cm, apex acuminate, smooth, densely hirtellous to velutinous.
erect on straight pedicels, narrowly fusiform, 5–8.5 × 0.4–0.7 cm, apex acuminate to attenuate, smooth, sparsely pilosulous to glabrate.
Asclepias obovata
Asclepias linearis
Asclepias obovata is a common milkweed of seasonally wet, sandy soils in pine woodlands of the Gulf Coastal Plain and (rarely) the southern Atlantic Coastal Plain. It is rare and considered to be of conservation concern in Arkansas.
(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.)
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