Whorls of narrow leaves circle the 8–24-inch tall, hairless stem of this erect, unbranched plant. Umbrella-shaped clusters of greenish-white flowers grow on short stems from the upper leaf axils.  Note the whorls of leaves do not have small, auxiliary shoots in the node. Sap is a milky latex.

FLOWERS: May–September. Rounded clusters (umbels) of up to 20 white flowers reach 2–3 inches wide. Each 1/4-inch tall and wide flower has 5 small petal-like lobes bent back against the stem with the tips spreading, and 5 white hoods with needle-shaped horns that arch toward the center column. Slender 2 1/2–4-inch long, erect pods dry and split open to release numerous seeds with fluffy tufts of hair to float on the wind.

LEAVES: Nodes with whorls of 4–8 leaves. The hairless, filament-like leaves reach 4–8-inches long (10–20 cm), 1/8-inch wide (3 mm), with a prominent midrib. No tiny leaf shoots grow in the axils. Milkweed leaves contain a high concentration of cardiac glycosides, which Monarch butterfly caterpillars concentrate to protect from bird predators.

HABITAT: Sandy, rocky soils of prairies, stream banks, fields, roadsides; desert grasslands and scrub, prairies, pinyon-juniper woodlands.

ELEVATION: 3,300–7,500 feet.

RANGE: Widespread throughout U. S. east of NM.

SIMILAR SPECIES: 32 species of milkweed grow in NM. The statewide Horsetail Milkweed, A. subverticillata,  has 3–4 narrow, linear leaves in a whorl around the stem, but often has tiny shoots in the axils.

NM COUNTIES: Scattered statewide in low- to mid-elevation habitats.