Asclepias obovata
Asclepias subulata
pineland milkweed
ajamete, candelilla, rush milkweed
1 (rarely more), erect to spreading, unbranched, 40–70(–200) cm, densely hirtellous to velutinous, not glaucous, rhizomes absent.
3–100 (usually few–numerous), erect to ascending, branched, especially in lower half, 50–175 cm, sparsely pilosulous to glabrate, thickly glaucous, rhizomes absent.
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.
ephemeral, often present on flowering stems, opposite (rarely whorled), sessile, with 0 or 1 stipular colleter on each side of leaf base;
blade filiform, 2–6 × 0.1 cm, succulent, base cuneate, margins entire, apex acute, mucronate, venation obscure, surfaces pilosulous, 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, pedunculate, 3–21-flowered;
peduncle 0.4–1.7 cm, sparsely pilose, glaucous, with 1 caducous bract at the base of each pedicel.
10–12 mm, densely hirtellous to velutinous.
11–21 mm, pilose.
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 spreading;
calyx lobes lanceolate, 4–4.5 mm, apex acute, pilose;
corolla green, sometimes tinged cream, yellow, or red, faintly striate, lobes reflexed, lanceolate, 7–12 mm, apex acute, glabrous;
gynostegial column 1–1.5 mm;
fused anthers brown, cylindric, 2–3 mm, wings right-triangular, distended at base, open at tip, apical appendages ovate;
corona segments cream, often tinged pink, yellow, or green, shiny, sessile, tubular, 7–9 mm, greatly exceeding style apex, base saccate, apex truncate, spreading, with proximal flaps, glabrous, internal appendage crested, apically falcate and sharply inflexed towards style apex, barely exserted, minutely papillose;
style apex shallowly depressed, cream to green.
broadly ovate, 8–9 × 6–7 mm, margin winged, faces smooth;
coma 2–5 cm.
flat to somewhat naviculate, ovate, 6–8 × 4–5 mm, margin narrowly winged, faces papillose-rugulose, concave face with a low keel;
coma 1.5–3 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.
pendulous on spreading pedicels, fusiform, 6.5–13.5 × 1–1.8 cm, apex acuminate, smooth, sparsely pilosulous or puberulent with curved trichomes to glabrate, glaucous.
= 22.
Asclepias obovata
Asclepias subulata
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.)
Morphological and ecological distinctions between Asclepias subulata and its close relative, A. albicans, are discussed under the latter species. The range of A. subulata is more extensive than A. albicans and is almost exactly confluent with that of the Sonoran Desert, although it extends into the southeastern part of the Mohave Desert. In Nevada, it is restricted to Clark and Lincoln counties. The elongate, tubular, cream corona segments are remarkably similar to those of A. nyctaginifolia. These species were formerly considered close relatives (R. E. Woodson Jr. 1954), but they are highly dissimilar morphologically, other than the corona segments. They appear to be only distantly related (M. Fishbein et al. 2011, 2018), and the corona similarities represent a remarkable convergence. Both species are commonly visited by long-tongued tarantula hawk wasps (Pompilidae, Pepsinae), but it is not known whether they are important pollinators for these milkweeds.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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