Niban 120x600 Mar2020

Pest Information

Mexican Whorled Milkweed

Mexican Whorled Milkweed

  • Latin Name: Asclepias Fascicularis
  • Common Name: Mexican Whorled Milkweed
  • Other Names: Narrow leaf milkweed, whorled milkweed

Pest Details

Mexican Whorled Milkweed
Mexican Whorled Milkweed


Native to Mexico and possibly western United States. Now widely distributed in the west at lower elevations.


Like most milkweeds it contains toxic chemicals, and can be injurious to livestock when eaten green or as a dry contaminant in hay. Milkweeds are the foodplants of the Monarch Butterfly and other species in the family Danaidae. A perennial broadleaf plant that can be found in almost any moist or dry situation. An extremely deep taproot allows it to survive in very dry situations. Growth is from seeds, or from creeping underground roots. The seeds have long, silky tufts of hair at their upper end, and when released by the wind may be carried long distances. Seeds germinate in the spring, along with regrowth of foliage from the roots, and the plants mature throughout the summer, with foliage dying in cold weather.


Mature plants may be as tall as 40 inches, with numerous green stems originating from root stocks at the base. Stems are nearly hairless. Leaves occur in whorls at nodes along the stem, with 3 to 6 leaves in a whorl. Leaves are dark green, and very long and narrow, perhaps 5 inches long. They have short stalks and are distinctly folded along the mid-vein. Flowers are pink to whitish and are in large clusters at the ends of long stalks. Each individual flower also is on a long stalk.

Characteristicts Important to Control:

Perennial with regrowth from spreading roots. Seed dispersal in the wind may carry seeds long distances.

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