Asclepias lemmonii
Asclepias hirtella
big-leaf milkweed, Lemmon's milkweed
asclépiade hérissée, green milkweed, prairie milkweed, tall green milkweed
1–3, erect to ascending, unbranched, very stout, 100–150 cm, densely hirsute, not glaucous, rhizomes absent(?).
1–3+, erect to spreading, unbranched (rarely branched), 30–125 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
opposite, petiolate, with 1 stipular colleter on each side of petiole;
petiole 1–5 mm, hirsute;
blade oval or oblong to ovate, 7–22 × 3–14 cm, subsucculent, base truncate to subcordate, margins entire, apex obtuse to truncate or emarginate, mucronate, venation brochidodromous, secondary veins nearly orthogonal, surfaces hirsute, margins ciliate, 8–16 laminar colleters.
opposite or alternate, sessile or petiolate, with 1–3 stipular colleters on each side of petiole, also in axil;
petiole 0–3 mm, puberulent with curved trichomes;
blade linear to linear-lanceolate, 4–16 × 0.2–1.5 cm, chartaceous, base cuneate, margins entire, apex acute to attenuate, mucronate, venation faintly brochidodromous, surfaces scabridulous to puberulent with curved trichomes, especially on veins, margins ciliate, laminar colleters absent.
terminal, paired, and extra-axillary, pedunculate, 21–53-flowered;
peduncle 6–13 cm, densely hirsute, with 1 caducous bract at the base of each pedicel.
extra-axillary, sessile or pedunculate, 34–112-flowered;
peduncle 0–4 cm, hirtellous, with 1 caducous bract at the base of each pedicel.
13–22 mm, densely hirsute.
11–23 mm, hirtellous.
erect to pendent;
calyx lobes lanceolate, 3.5–6 mm, apex acute, hirsute;
corolla cream to greenish cream or ochroleucous, sometimes tinged pink, lobes reflexed with spreading tips, elliptic, 9–11 mm, apex acute, glabrous;
gynostegial column 0.5–1 mm;
fused anthers greenish brown, cylindric, 2.5–3 mm, wings right-triangular, closed, apical appendages oval;
corona segments cream to ochroleucous, sometimes tinged pink, shiny, subsessile, conduplicate, 6–8 mm, equaling or exceeding style apex, apex truncate, spreading and tapering, glabrous, internal appendage laterally compressed, erect, barely exserted, glabrous;
style apex shallowly depressed, green or pink.
erect to pendent;
calyx lobes lanceolate, 1.5–2 mm, apex acute, hirtellous;
corolla green to greenish cream, red-violet at tip, lobes reflexed, oblong, 3–5 mm, apex obtuse, glabrous;
gynostegial column 0.5–1 mm;
fused anthers green, cylindric, 1–1.5 mm, wings trapezoidal, closed, apical appendages oblate;
corona segments cream to greenish cream, rarely pinkish lavender or brown, often with a dorsal red-violet stripe or at base, sessile, laminar, strongly dorsally compressed, margins incurved, appressed to column, saccate, 1.5–2 mm, not exceeding point of anther wings, greatly exceeded by style apex, apex truncate, glabrous, internal appendage absent or obscure, glabrous;
style apex shallowly depressed, green.
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose;
coma 4–4.5 cm.
ovate, 10–11 × 7–8 mm, margin winged, faces smooth;
coma 3.5–4 cm.
erect on upcurved pedicels, lance-ovoid, 9.5–13.5 × 2–3 cm, apex attenuate, smooth, densely hirsute.
erect on upcurved pedicels, fusiform, 6–15 × 1–2 cm, apex attenuate, smooth, pilosulous to puberulent with curved trichomes.
Asclepias lemmonii
Asclepias hirtella
A highly distinctive species, Asclepias lemmonii just barely enters the United States in southern Arizona (Cochise, Pima, and Santa Cruz counties), where it inhabits canyons in pine-oak clad sky-island ranges. Asclepias elata is a common co-inhabitant of these canyons. Asclepias lemmonii has been documented from the Baboquiviri, Chiricahua, Huachuca, and Santa Rita mountains, and it is not common in any of these. It is considered to be of conservation concern in Arizona. The large, hirsute leaves with nearly orthogonal venation and robust, hirsute stems of A. lemmonii are unmatched among American milkweeds. Plants may reach heights over 2 m in the main range of the species in the northern Sierra Madre Occidental.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asclepias hirtella has been included sometimes in a broadly circumscribed A. longifolia. The species are parapatric and usually are readily distinguished by the hirtellous pedicels of A. hirtella and puberulent pedicels with curved trichomes of A. longifolia. Asclepias hirtella is also typically much taller with more numerous umbels compared to A. longifolia. However, populations along the Gulf Coastal Plain from eastern Texas to the Mississippi River and from southern Mississippi to central Georgia have proved challenging because they include plants with the growth form of A. longifolia and the pedicel vestiture of A. hirtella. Consequently, these populations have not been consistently assigned to one species or the other. However, the previously overlooked difference in corona segment length correlates perfectly with the pedicel vestiture and with geography. Thus, Gulf Coast populations west of the Mississippi River and north of the immediate coastline are here interpreted to represent short-statured A. hirtella. This hypothesis warrants investigation with population genetic data—it is quite possible that populations of A. hirtella in southern Arkansas, Louisiana, and Texas merit recognition as a subspecies. Asclepias hirtella is rare at the margins of its range and is considered to be of conservation concern in Georgia, Kentucky, Louisiana, Michigan, Minnesota (Mower County), Mississippi, Tennessee, West Virginia (Jackson, Mason, and Putnam counties), and Ontario (Essex County).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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