Asclepias obovata
Asclepias elata
pineland milkweed
nodding milkweed
1 (rarely more), erect to spreading, unbranched, 40–70(–200) cm, densely hirtellous to velutinous, not glaucous, rhizomes absent.
1 (rarely 2 or 3), erect, unbranched, 30–80 cm, glabrous, 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 inconspicuous stipular colleter on each side of leaf base;
blade oval or elliptic to oblong or lanceolate, 5.5–14 × 1.5–6 cm, subsucculent, base cordate, clasping, margins sometimes crisped, apex rounded to acute, mucronate, venation brochidodromous, surfaces glabrous, glaucous, margins minutely and remotely 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.
terminal and extra-axillary at upper nodes, pedunculate, 7–20-flowered;
peduncle 5–20 cm, pilosulous in a line, glaucous, with 1 caducous bract at the base of each pedicel.
10–12 mm, densely hirtellous to velutinous.
20–32 mm, pilosulous, often in a line.
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.
pendent;
calyx lobes elliptic to oval, 5–8 mm, apex acuminate, sparsely pilosulous to glabrate;
corolla green, lobes reflexed with spreading tips, oval, 11–14 mm, apex acute, glabrous;
gynostegium sessile;
fused anthers green, obconic, 3–3.5 mm, wings narrowly right-triangular, thick, open just above base, apical appendages lanceolate;
corona segments white, yellow to tan dorsally, subsessile, conduplicate, 4–6 mm, equaling style apex, apex truncate, glabrous, internal appendage a crest, included in segment, glabrous;
style apex depressed, green to greenish cream.
broadly ovate, 8–9 × 6–7 mm, margin winged, faces smooth;
coma 2–5 cm.
ovate to lanceolate, 6–7 × 3–6 mm, margin winged, sometimes minutely erose, faces rugulose;
coma 4–4.5 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 upcurved pedicels, fusiform to lance-ovoid, 8–13 × 1–2 cm, apex long-attenuate, smooth, pilosulous.
Asclepias obovata
Asclepias elata
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.)
Asclepias elata is one of the few milkweeds in the flora area that possesses a mostly Mexican distribution but does not belong to the major clade that contains most of such species (species 23–27 here). Rather it is the sole representative in the flora, and the most northerly distributed member, of a small clade of glaucous, vegetatively homogeneous species ranging as far south as Costa Rica (M. Fishbein et al. 2011). Asclepias elata has been inconsistently recognized as distinct from A. glaucescens since the time of A. Gray et al. [1878–1897, vol. 2(1)]. However, at least since J. N. Rose (1892), the distinction between these species has been understood, and was presented clearly by R.E. Woodson Jr. (1954). Although indistinguishable in the absence of flowers, A. elata differs by fully pendent (versus erect to pendent) flowers, fewer flowers per umbel, longer corolla lobes, and corona segments that spread away from the gynostegium and are exceeded by the style apex, with the appendage merely a crest included in the segment (versus segments that are strict, overtop the style apex, and bear exserted appendages in A. glaucescens). Both species have extensive distributions, but they are largely allopatric, except in Mesoamerica. The northernmost populations of A. glaucescens are in Nayarit and San Luis Potosí. Asclepias elata is one of a cohort of species reaching their northwestern limits in Arizona that indicate biogeographic affinity of that region to the eastern slope of the Sierra Madre Occidental and Altiplano, rather than the western slope of the Sierra Madre Occidental. Other examples from the milkweed flora include A. brachystephana, A. involucrata, A. nummularia, A. oenotheroides, and A. quinquedentata. In Arizona, A. elata is known from Cochise, Graham, Pima, and Santa Cruz counties, in New Mexico from Eddy, Hidalgo, and Sierra counties, and in Texas from Brewster, Culberson, Jeff Davis, and Presidio counties.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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