Plant: Perennial rhizomatous herb, erect or ascending, unbranched or branching, frequently also with dwarf, lateral shoots in at least some of the leaf axils, 20-100 cm tall, glabrous or finely pubescent above; milky sap
Leaves: whorled, mostly 3 or 4 per node, subsessile, the petioles 1-4 mm long, the blades linear, 2-12 cm long, ca. 1-4 mm broad, attenuate and acute at apex and base, essentially glabrous on both surfaces, the margins more or less revolute
INFLORESCENCE: UMBELS lateral to subterminally crowded, single or paired at the upper nodes, 2-4 cm broad, the peduncles mostly 1-5 cm long
Flowers: small; calyx lobes ca. 2 mm long; corolla white, greenish, or grayish purple, the lobes 4-5 mm long; hoods white or yellowish, erect-ascending, quadrate to oblong-obovoid, 1.4-2.4 mm long, 0.8-1.6 mm broad at the truncate to oblique rim, about as long as to 1 mm shorter than the gynostegium, the horns radially flat, attached near the base of the hoods, exserted 1-2 mm and arching over the stigma head; anther wings 1.4-1.6 mm long; corpusculum ca. 0.25 mm long, the pollinia 0.8-1.2 mm long
Fruit: FOLLICLES erect on erect pedicels, 6-12 cm long
Misc: Open woodlands, grasslands, stream terraces, invading roadsides, pastures, yards and gardens; 950-2400 m (3100-7800 ft); Jun-Sep
REFERENCES: Sundell, Eric. 1994. Asclepiadaceae. J. Ariz. - Nev. Acad. Sci. Volume 27, 169-187.
Duration: Perennial
Nativity: Native
Lifeform: Forb/Herb
General: Herbaceous perennial, 15-100 cm tall; stems numerous, erect to ascending, unbranched or branched, from stout woody rhizomes; herbage glabrous or finely pubescent above.
Leaves: Whorled with 3-4 leaves per node, subsessile with petioles to 4 mm; blades linear, 2-12 cm long, 1-4 mm wide, glabrous or nearly so, the margins generally revolute.
Flowers: Small and white, in solitary umbels 2-4 cm across, on peduncles 1-5 cm long at the upper nodes; corolla white to cream colored or even greenish-purple, the lobes 3-5 mm long; the hoods white to yellowish, about 2 mm long, erect-ascending, 1-3 mm long, with a truncate to oblique rim; horns longer than hoods; calyx lobes about 2 mm long.
Fruits: Narrowly fusiform follicle, 5-12 cm long, on erect pedicels.
Ecology: Found in open areas, generally in woodlands, grasslands, to disturbed areas from 3,000-8,000 ft (914-2438 m); flowers June-September.
Distribution: ID, NV, CA east to TX, OK and KS; south to s MEX.
Notes: Distinguished by the erect, rhizomotous growth form; the whorled, linear leaves; and the umbels with white, generally small flowers for a milkweed. Very similar to A. fascicularis and A. verticillata. Sundell 1993 refers to these three species as being essentially a continuum from west to east with this species in the middle. Can be difficult to distinguish, but A. verticillata generally has more leaves per node and A. fascicularis is generally not found outside of the Pacific states. Of the milkweed species native to the Desert Southwest, A. subverticillata often ranks among the most toxic to free-ranging livestock; it is also a known monarch host plant.
Ethnobotany: Used to help stimulate breast milk; seed silk used; the first buds eaten; the pods were eaten, used for clothing, and made into prayer sticks. Often considered to be highly poisonous.
Etymology: Asclepias is named for the Greek god of healing Asklepios, while subverticillata means not quite whorled.
Synonyms: Asclepias galioides
Editor: SBuckley 2011, 2014, FSCoburn 2015, AHazelton 2015
