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Manitoba Museum

Milkweed (Asclepiadaceae)

Swamp Milkweed

Asclepias incarnata L.

Swamp Milkweed is named for its milky white sap and high moisture requirements. It is a fragrant plant, and toxic when consumed in large doses. Plants have been used by Indigenous peoples for medicinal purposes, and its stem fibres were used for making rope and textiles. The fluffy seed hairs drift on the wind and float on water. These seeds were used during WWII for stuffing in pillows and lifejackets.

Flower Colour:

  • Pink

Flowering Season:

  • Summer

Flowering Months:

  • August
  • July
  • June

Canadian Rarity Status:

Not rare. Listed as “may be at risk” on Prince Edward Island.

Physical Appearance:

This perennial grows between 30 and 150 cm tall, with stems occasionally branching. The leaves are opposite, and lance-shaped with smooth edges. Flowers occur in clusters of 10-40 on stem-tops. Each flower has five drooping pink petals, partially joined at their base. Between these and the stamens are five light pink, hooded arches, each with a curved horn. In the fall, seeds with tufts of hair are released from tear-shaped fruits and distributed by the wind.

Similar Species:

Dwarf Milkweed, Showy Milkweed

Gardening Notes:

Seeds and/or plants are typically available from greenhouses and seed supply companies specializing in native plants. Swamp Milkweed can be grown from seed or by dividing already established plants.

Canadian Distribution:

  • Manitoba
  • New Brunswick
  • Nova Scotia
  • Ontario
  • Prince Edward Island
  • Quebec

Prairie Types:

  • Tall Grass Prairie


  • Forests
  • Prairies
  • Roadsides
  • Wetlands

Moisture Conditions:

  • Moderate
  • Moist
  • Wet

Light Preference:

  • Full Sun
  • Part Shade

Soil Preference:

  • Acidic
  • Clay
  • Loam
  • Neutral
  • Silt
Swamp Milkweed