Asclepias cordifolia
Asclepias rubra
heart-leaf milkweed, purple milkweed
red milkweed
1–20, ascending to spreading, unbranched, 25–100 cm, glabrous, glaucous, rhizomes absent.
1, erect, unbranched, 40–110 cm, puberulent in a single line with curved trichomes to glabrate, somewhat glaucous, rhizomes absent.
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 stipular colleter on each side of petiole on a ciliate interpetiolar ridge;
petiole 1–2 mm, glabrous;
blade narrowly lanceolate to ovate, 5–16 × 1–4.5 cm, chartaceous, base cordate, margins entire, apex attenuate, venation brochidodromous, surfaces glabrous, somewhat glaucous, margins ciliate, 6–8 laminar colleters, usually obscured by conduplicate petiole.
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.
terminal, usually branched, sometimes also extra-axillary at 1 upper node, pedunculate, 9–20-flowered;
peduncle 0.5–13 cm, puberulent in 1 line with curved trichomes, with 1 caducous bract at the base of each pedicel.
16–37 mm, sparsely pilose.
11–17 mm, puberulent on 1 side with curved trichomes.
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;
calyx lobes lanceolate, 2–2.5 mm, apex acute, glabrous;
corolla pink to reddish purple, lobes reflexed with spreading tips, elliptic, 7–9 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1.5–2 mm;
fused anthers green, cylindric, 2–2.5 mm, wings right-triangular, closed, apical appendages broadly ovate;
corona segments pink to lavender, stipitate, conduplicate, dorsally flattened, 6–7 mm, greatly exceeding style apex, apex acute, glabrous, internal appendage subulate, exserted, arching above style apex, glabrous;
style apex shallowly depressed, green.
ovate, 8–9 × 5–7 mm, margin not winged, faces reticulate-rugulose;
coma 3–3.5 cm.
ovate, 7–9 × 5–7 mm, margin winged, faces minutely rugulose to smooth;
coma 2–5 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, narrowly fusiform, 7–12 × 1–1.5 cm, apex long-acuminate, smooth, sparsely puberulent with curved trichomes or pilosulous to glabrate.
= 22.
Asclepias cordifolia
Asclepias rubra
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.)
Distinguishing features and hybridization of Asclepias rubra and A. lanceolata are discussed under the latter species. The common name red milkweed is a misnomer, as the flowers are actually more commonly shades of pink or purple, whereas the similar A. lanceolata often has truly red corollas. Asclepias rubra is less common than A. lanceolata and considered to be of greater conservation concern in Alabama, Delaware, Georgia, Maryland, New Jersey, and Virginia. It is considered to be extirpated from the District of Columbia, New York, and Pennsylvania. It also has been reported from Arkansas, but this remains unconfirmed and must be considered unlikely.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
CA
OR
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