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Ministry of Agriculture, Food and Rural Affairs


Scientific Name: Asclepias syriaca L.

Other Names: asclépiade de Syrie, cotonnier, petit-cochon

Family: Milkweed Family (Asclepiadaceae)

General Description: Perennial, reproducing by seed and by horizontally spreading underground roots which produce new leafy stems. The whole plant, root, stem, leaves, flowers and fruit, contain abundant, thick, white, milky juice.

Habitat: Common milkweed occurs throughout southern Ontario in pastures, meadows, waste places, roadsides and cultivated land. It is especially common in the Manitoulin Islands and the east-central portions of southern Ontario, but it seems to be increasing in most other portions of the province as well.



  • Erect,
  • 1-2 m (3-6½ ft) high,
  • Stout,
  • Unbranched or sometimes with 1 or 2 branches near the top,
  • Usually several stems close together from the underground root system.


  • Opposite (2 per node) or whorled (3 or more per node),
  • Oblong with a rounded or tapered base and a rounded to somewhat pointed tip,
  • Without teeth,
  • Underside covered with fine velvety hair,
  • Upper surface usually without hair and deeper green.


  • In dense, nearly spherical clusters or umbels at the tip of the stem and from axils or upper leaves,
  • Each flower 8-10 mm (1/4-2/5 in.) across,
  • Greenish to purplish or whitish,
  • 5 thin sepals and 5 larger petal lobes bent back along the flower stalk,
  • An unusual arrangement of 5 hoods and horns forming a crown or corona around the top of each flower,
  • Uniquely adapted for insect pollination, having waxy pollen in tiny wishbone-shaped structures,
  • Flowers from mid-June to August.


  • At first:
    • Green,
    • Fleshy,
    • 7-10 cm (2 ½-4 in.) long and ¼ to ½ as wide,
    • Covered with soft, warty protuberances.
  • Later:
    • Brown,
    • Splitting lengthwise along a single opening and releasing numerous seeds,
    • Usually only 1 or 2 (rarely up to 5) seedpods develop from the many flowers of a single flower cluster.
  • Seeds:
    • Flat,
    • Oval,
    • With a tuft of long silky hair at one end,
    • Matures seed from August to October.

Often Confused With
It is distinguished by its pairs of broad, oval, softly hairy leaves, umbels of purplish to whitish flowers with their peculiar arrangement of parts, and the large, thick, softly warty seedpods.

Caution: Other species of milkweed have been found to be highly toxic to livestock, and circumstantial evidence suggests Common milkweed may, under some circumstances, also be toxic.

Common milkweed. A. Top of flowering plant. B. Seedpods with 1 open and showing it's layers of seeds with their tufts of long silky hairs. Common milkweed Common milkweed Common milkweed Common milkweedClick to enlarge.