Ontario Weeds: Swamp milkweed

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  5. Stems and Roots
  6. Flowers and Fruit
  7. Habitat
  8. Similar Species
  9. Caution
  10. Related Links

Name: Swamp milkweed Asclepias incarnata L.,

Other Names: asclépiade incarnate

Family: Milkweed Family (Asclepiadaceae)

General Description: Perennial, reproducing by seed and possibly by rhizomes.

Photos and Pictures

Swamp milkweed.

Swamp milkweed.

Swamp milkweed. B. Flowering stem with 10 simple umbels

Swamp milkweed. B. Flowering stem with 10 simple umbels.

Swamp milkweed. A. Base of plant. C. Two seedpods from 2 flowers of 1 umbel.

Swamp milkweed. A. Base of plant. C. Two seedpods from 2 flowers of 1 umbel.

Stems & Roots: Stems erect, stout, 30-150cm (12-60in.) high, with little milky juice and few, if any, hairs; leaves opposite, rather numerous, lanceolate to elliptic, 4.5-20cm (1¾-8in.) long with fine veins clearly visible on the underside.

Flowers & Fruit: Inflorescence broad, usually formed from several umbels of flowers; flowers pink to rose-purple (rarely whitish), similar to those of Common milkweed but more slender; fruits slender pods with elongated tips, rusty-green, splitting lengthwise at maturity; seeds brown, flat, with winged margins and tufts of long, silky, white hair. Flowers from June to August.

Habitat: Swamp milkweed is found in swamps, ditches and other wet areas in woods, fields and roadsides in southern and central Ontario.

Similar Species: It is distinguished from other milkweeds by its numerous, slender leaves, its pink to rose-purple flowers and its slender, non-warty pods, and from other narrow-leaved plants by its smooth stems, slender, opposite leaves and somewhat milky juice.

Caution: It is considered poisonous to livestock.

Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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