WILDFLOWERS OF NEW MEXICO

 
 

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. 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.

WHORLED  MILKWEED

ASCLEPIAS  VERTICILLATA

Dogbane Family, Apocynaceae (formerly Milkweed Family, Asclepiadaceae)

Perennial herb

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  1. 1.Petal-like lobes (lower arrow).

  2. 2. Hood of flower (middle arrow).

  3. 3. Horns inside hoods (upper arrow).

Photo © UW-System WisFlora. Creative Commons

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