Asclepias cordifolia
Asclepias arenaria
heart-leaf milkweed, purple milkweed
sand milkweed
1–20, ascending to spreading, unbranched, 25–100 cm, glabrous, glaucous, rhizomes absent.
1–8, spreading or decumbent to erect, unbranched or rarely branched near base, 20–100 cm, tomentose, not glaucous, rhizomatous.
opposite, sessile, stipular colleters absent;
blade ovate to lanceolate, 3.5–11 × 1.8–8 cm, chartaceous, base cordate, clasping, margins entire, apex acute, mucronate, venation brochidodromous to eucamptodromous, surfaces glabrous, glaucous, margins minutely ciliate, laminar colleters absent.
opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole plus 0–4 in axil;
petiole 7–17 mm, tomentose;
blade oblong or obovate to ovate or oval, 4.2–11.5 × 2.5–7.5 cm, subcoriaceous, base rounded or truncate to subcordate, margins often undulate or crisped, apex truncate to rounded (rarely acute), sometimes emarginate, often mucronate, venation brochidodromous, surfaces tomentose to nearly glabrate, margins ciliate, 12–24 laminar colleters.
terminal, branched, sometimes also extra-axillary at upper nodes, pedunculate, 5–20-flowered;
peduncle 0.3–6.5 cm, apically sparsely pilose to glabrate, with few bracts.
extra-axillary (sometimes appearing terminal), sessile or pedunculate, 14–51-flowered;
peduncle 0–2 cm, tomentose, with 1 caducous bract at the base of each pedicel.
16–37 mm, sparsely pilose.
15–25 mm, densely tomentose.
erect to pendent;
calyx lobes elliptic to lanceolate, 3–5 mm, apex acute, pilose;
corolla red-violet, lobes reflexed with spreading tips, oval, 6–7 mm, apex acute, glabrous;
gynostegial column 1–1.5 mm;
fused anthers brown, cylindric, 1.5–2 mm, wings right-triangular, open at tip, apical appendages deltoid;
corona segments white, tinged pink to red-violet at base, sessile, tubular, 2–3 mm, exceeded by style apex, base saccate, apex truncate, oblique, glabrous, internal appendage absent;
style apex shallowly depressed, pink to red-violet.
erect to pendent;
calyx lobes lanceolate, 2.5–3 mm, apex acute, densely tomentose;
corolla green to yellowish green, sometimes tinged reddish or purplish, lobes reflexed with spreading tips, oval, 7–8 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1–2 mm;
fused anthers green, obconic, 2–2.5 mm, wings right-triangular, closed, apical appendages ovate;
corona segments cream to greenish cream or ochroleucous, subsessile, conduplicate, flaring at base, 3.5–4 mm, exceeding style apex, apex truncate to rounded, emarginate, minutely papillate, proximal margin toothed, internal appendage falcate, exserted, sharply incurved over style apex, apex upturned, minutely papillose.
ovate, 8–9 × 5–7 mm, margin not winged, faces reticulate-rugulose;
coma 3–3.5 cm.
oval, 9–12 × 6–8 mm, margin winged, faces minutely rugulose;
coma 2–3 cm.
erect on upcurved pedicels, lance-ovoid, 7.5–10.5 × 1.5–1.8 cm, apex long-acuminate, smooth, glabrous, glaucous.
erect on upcurved pedicels, lance-ovoid, 5.5–10 × 2–2.8 cm, apex acuminate, smooth, pilosulous.
= 22.
Asclepias cordifolia
Asclepias arenaria
Fresh leaves and stems of Asclepias cordifolia are often slightly or strongly colored bluish, grayish, or purplish. This is one of the few American species of Asclepias with cavitate corona segments that lack adaxial appendages. Such species were segregated along with diverse African species in Gomphocarpus R. Brown, a polyphyletic segregate (M. Fishbein et al. 2011; D. Chuba et al. 2017). Asclepias cordifolia is a distinctive species unlike any other within its range. It is phylogenetically and geographically isolated, although not highly derived morphologically. In Nevada, A. cordifolia is restricted to the Sierra Nevada, in Carson City, Douglas, and Washoe counties. Its range extends to northern California and southwestern Oregon.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asclepias arenaria is the milkweed most consistently associated with pure sand soils in the western Great Plains. It is predictably found at the bases of stabilized and semi-stabilized dunes. Flowers of this species are visited by a variety of Hymenoptera, notably several species of large wasps, including tarantula hawk wasps (Pepsinae, Pompilidae) and scoliid wasps (Scoliidae), as well as by Lepidoptera. Non-flowering shoots of A. arenaria may produce linear leaves; they are easily overlooked and not identified as belonging to this species unless one is aware of this variation, especially when they are produced on rhizomes distant from shoots with typical foliage. This trait is found in several other broad-leaved milkweeds (for example, A. erosa, A. welshii). Asclepias arenaria is rare and considered to be of conservation concern in Wyoming, where it has been recorded from only two sites in Goshen County.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
CA
OR
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
KS Wildflowers
