Ontario Weeds: Common milkweed
Excerpt from Publication 505, Ontario Weeds,
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Table of Contents
- Other Names
- General Description
- Stems and Roots
- Flowers and Fruit
- Similar Species
- Related Links
Name: Common milkweed, Asclepias
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.
Common milkweed. A. Top of flowering plant. B. Seedpods with 1 open and showing its layers of seeds with their tufts of long silky hairs.
Stems & Roots: Stems erect, 1-2m
(3-6½ft) high, stout, unbranched or sometimes with 1 or 2
branches near the top, usually several stems close together from
the underground root system; leaves 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
Flowers & Fruit: Flowers in dense, nearly spherical clusters or umbels at tip of stem and from axils of upper leaves, each flower 8-10mm (¼-2/5in.) across, greenish to purplish or whitish, with 5 thin sepals and 5 larger petal lobes bent back along the flower stalk and an unusual arrangement of 5 hoods and horns forming a crown or corona around the top of each flower. The flowers are uniquely adapted for insect pollination, having waxy pollen in tiny wishbone-shaped structures which hook onto an insect's leg but come off when transferred to the flower of a different plant. Fruits at first green, fleshy, 7-10cm (2½-4in.) long and ¼ to ½ as wide, covered with soft, warty protuberances, later turning 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; seed flat, oval, with a tuft of long silky hair at one end. The whole plant, root, stem, leaves, flowers and fruit, contain abundant, thick, white, milky juice. Flowers from mid-June to August, and matures seed from August to October.
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.
Similar Species: 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.
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