Ontario Weeds: Clasping-leaved dogbane

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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. Leaves
  7. Flowers and Fruit
  8. Habitat
  9. Similar Species
  10. Caution
  11. Related Links

Name: Clasping-leaved dogbane Apocynum sibiricum Jacq.,

Other Names: apocyn a feuilles embrassantes, Indian hemp, Prairie dogbane, chanvre sauvage

Family: Dogbane Family (Apocynaceae)

General Description: Resembles both Spreading dogbane and Indian hemp and before flowering is easily confused with Common milkweed. Perennial from deeply penetrating and widely spreading coarse roots, these often 20-30cm (8-12in.) below the surface.

Photos and Pictures

Clasping-leaved dogbane, showing deep perennial root from which 4 shoots emerged.

Clasping-leaved dogbane, showing deep perennial root from which 4 shoots emerged.

Clasping leaved dogbane. C. 3 shoots forma deep, coarse perennial root (dotted line represents ground surface), and leaves on lower portion of 1 shoot.

Clasping leaved dogbane. C. 3 shoots forma deep, coarse perennial root (dotted line represents ground surface), and leaves on lower portion of 1 shoot.

Stems & Roots: Stems coarse, erect, up to 1m (40in.) tall, arising from buds on the roots; the main stem with branches throughout its length, smooth and hairless, green or with a slight pinkish cast.

Leaves: Leaves usually opposite but occasionally alternate, mostly sessile or with very short petioles (usually not more than 3-5mm, 1/8-1/5in. long), up to 5cm (2in.) wide and 12cm (4¾in.) long or sometimes larger, oblong to broadly elliptic with a somewhat abruptly pointed tip and a broadly rounded to heart-shaped base, smooth and hairless on both surfaces, the undersurface lighter green than the upper; the basal lobes of the larger leaves somewhat clasping the stem.

Flowers and Fruit: Inflorescence, flowers and seedpods similar to those of Spreading dogbane except that the calyx lobes of Clasping-leaved dogbane are narrow and 3-5 times longer than wide, and its corolla is white and usually only 3-6mm (1/8-¼in.) long. All parts of the plant contain milky juice. Flowers from July to September.

Habitat: Clasping-leaved dogbane is also a native plant with much the same distribution and abundance as Spreading dogbane

Similar Species: It is distinguished from both Spreading dogbane and Indian hemp by the lower leaves on its main stem and lower branches having heart-shaped bases that more or less clasp the stem, and the petioles of all leaves being very short or almost absent; and, from Spreading dogbane by the undersides of its leaves being virtually hairless, even along the midribs, as well as by its smaller white flowers having very narrow sepals. It is distinguished from Common milkweed by its lighter green leaves having abruptly pointed tips and being virtually hairless (those of milkweed being somewhat bluish-green, more rounded at the tip, and finely velvety hairy on the undersurface); by its loosely branching inflorescence (not an umbel) with small white flowers, and by its pencil-thin seedpods.

Caution: May be 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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