Asclepias tuberosa |
Asclepias lemmonii |
|||||||||
---|---|---|---|---|---|---|---|---|---|---|
asclépiade tubéreuse, butterfly milkweed |
big-leaf milkweed, Lemmon's milkweed |
|||||||||
Habit | Herbs. | Herbs. | ||||||||
Stems | 1–numerous, erect to ascending, branched in inflorescence, 15–90 cm, densely hirsute, not glaucous, rhizomes absent. |
1–3, erect to ascending, unbranched, very stout, 100–150 cm, densely hirsute, not glaucous, rhizomes absent(?). |
||||||||
Leaves | alternate, petiolate, with 1 or 2 stipular colleters on each side of petiole; petiole 1–4 mm, densely hirsute; blade elliptic, oblong, or oblanceolate to lanceolate or linear, 2–12 × 0.3–3 cm, chartaceous, base cuneate or obtuse to rounded, truncate, hastate, or cordate, margins entire, apex acute to attenuate or obtuse to rounded, venation brochidodromous to eucamptodromous, surfaces hirsute, more densely so on midvein abaxially, margins ciliate, 0–4 laminar colleters. |
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. |
||||||||
Inflorescences | corymbs of extra-axillary umbels on branches, sessile or pedunculate, 5–27-flowered; peduncle 0–4 cm, sometimes branched, hirsute, with 1 caducous bract at the base of each pedicel. |
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. |
||||||||
Pedicels | 9–24 mm, puberulent with curved trichomes to pilosulous. |
13–22 mm, densely hirsute. |
||||||||
Flowers | erect; calyx lobes narrowly lanceolate, 2–3 mm, apex acute, hirsute to puberulent with curved trichomes; corolla reddish orange (nearly red) to orange or yellow, lobes reflexed with spreading tips, narrowly elliptic, (5–)6–8 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1.2–1.5 mm, fused anthers yellow to yellowish green, cylindric, 2–3 mm, wings right-triangular, closed, apical appendages ovate; corona segments reddish orange (nearly red) to orange or yellow, substipitate, conduplicate, dorsally flattened, sulcate, 5.5–7 mm, greatly exceeding style apex, apex acute, glabrous, internal appendage subulate, exserted, arching above style apex, glabrous; style apex shallowly depressed, yellow to yellowish green. |
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. |
||||||||
Seeds | ovate, 8–9 × 4–5 mm, margin winged, faces minutely rugulose; coma 3–5 cm. |
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose; coma 4–4.5 cm. |
||||||||
Follicles | erect on upcurved pedicels, fusiform, 7–14 × 1.2–2 cm, apex long-acuminate or attenuate, smooth, hirsute. |
erect on upcurved pedicels, lance-ovoid, 9.5–13.5 × 2–3 cm, apex attenuate, smooth, densely hirsute. |
||||||||
2n | = 22. |
|||||||||
Asclepias tuberosa |
Asclepias lemmonii |
|||||||||
Phenology | Flowering Jun–Sep; fruiting Aug–Oct. | |||||||||
Habitat | Canyons, slopes, streamsides, rocky and clay soils, pine-oak, pine, and riparian forests, oak woodlands, marshes. | |||||||||
Elevation | 1200–2200 m. (3900–7200 ft.) | |||||||||
Distribution |
North America; n Mexico
|
AZ; Mexico (Chihuahua, Durango, Jalisco, Sonora, Zacatecas)
|
||||||||
Discussion | Subspecies 3 (3 in the flora). Asclepias tuberosa is one of the most familiar and beloved North American milkweeds and is a favored element of pollinator gardens because of the cheery orange flowers that attract abundant insect visitors. The clear latex is unusual in the genus and is often commented upon by collectors. The subspecies of A. tuberosa are highly intergrading. It is often difficult to satisfactorily place a given specimen in a particular subspecies; however, the great majority are readily assigned. It appears that the conspicuous variation in leaf morphology across the subspecies corresponds to genetically structured population variation (R. E. Woodson Jr. 1947). However, it is unknown to what extent cultivation and other human activities have blurred the distinctions among the geographic variants. Future recognition of the subspecies should be supported by genetic study with modern techniques. Although yellow-flowered plants predominate in the western plains, color variation is often pronounced in single populations, and yellow flowers may be encountered anywhere in the range. Hybridization with A. syriaca is documented, but is exceedingly rare. Presumed hybrids can be recognized by intermediate floral and vegetative traits. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
||||||||
Key |
|
|||||||||
Source | FNA vol. 14. | FNA vol. 14. | ||||||||
Parent taxa | Apocynaceae > Asclepias | Apocynaceae > Asclepias | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Name authority | Linnaeus: Sp. Pl. 1: 217. (1753) | A. Gray: Proc. Amer. Acad. Arts 19: 85. (1883) — (as lemmoni) | ||||||||
Web links |