Milkweed Fact Sheet

Milkweed Facts

Common Name: Common milkweed
Scientific Name: Asclepias syriaca

Milkweed usually has a solitary, simple stem, 0.5-1.8 meters (1.5-6 feet) tall, though clumps of multiple stems can be found. Leaves are opposite, oval, and 5-25 centimeters (2-10 inches) long. The surface of the leaf is hairy underneath and smooth on top. The leaf stem is short and thick. Milkweed may also send up stems intermittently through the growing season. This may result in stems being at different lifestages throughout the summer.

Special Characteristics: Milkweed exudes a thick white sap from any cut or broken surface.

Habitat: Milkweed is common in fields, meadows and along roadsides.

Range: Milkweed is found from New Brunswick to Saskatchewan, south to Georgia and Tennessee and west to Iowa and Kansas.

Propagation: Milkweeds flower from June to August. The flower consists of a large cluster of individual flowers on a stalk. A flower stalk may originate from the tip of a branch or stem or at the junction of a leaf with a stem. Insects usually pollinate the flowers because the pollen is lumped in waxy masses that are too sticky and heavy for wind fertilization. Very few of the flowers produce large, healthy seed pods. The seeds are dispersed by the wind catching the long silky hairs. Studies of seed dispersal indicate seeds typically drift 7.5 to 30 meters (25 to 100 feet) before settling to the earth.

Milkweed also propagates from underground rhizomes, which may be several meters in length. A rhizome may produce multiple stems, so numerous stems within a short distance (e.g., 0.5-1.0 meters) of each other may all be from the same rhizome. These multiple stems are genetically identical and the clump can be referred to as a clone.

Life Span: Milkweed may live as little as 2 to 3 years or as long as 25 years.

Threats to the Milkweed: Most species of milkweed are not seriously threatened, although one type of milkweed is on the endangered species list.

Some potential threats to the milkweed family:

  • Milkweed is considered a weed in many areas, resulting in frequent, sometimes large-scale attempts to get rid of it.
  • Some strains of milkweed are sensitive to a form of air pollution called ground-level ozone, a.k.a. smog. This pollutant reacts chemically with the milkweed plant to damage its leaves. Studies have not shown major ozone-related reduction in milkweed populations.