Ontario Weeds: White snakeroot

Table of Contents

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

Name: White snakeroot, Eupatorium rugosum Houtt.

Other Names: EUPRU, epuatoire rugueuse eupatore à feuilles d'ortie

Family: Composite or Aster Family (Compositae) 

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

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Photos and Pictures

White snakeroot.

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Stems & Leaves: Stems erect, slightly hairy, rising 0.2 - 1.5 m (8 - 60 in.) high from knotty, tough rhizome; leaves opposite, ovate, longer than broad, the larger ones being 5 - 18 cm (2 - 7 in.) long and 3 - 12 cm ( 1 1/4 - 5 in.) wide, with sharply and coarsely toothed margins and acuminate tips.

Flowers & Fruit: Petioles 1/4 to 1/3 the length of the leaf blade; inflorescence of well-developed plants composed of several loosely branched, more or less flat-topped corymbs of flower heads that arise from the axils of the upper leaves; each flower head about 6 mm (1/4 in) long and nearly as wide, with 12 to 30 bright white florets per head; all florets are tubular (it has no ray or ligulate florets); "seeds" (achenes) slender, cigar-shaped, about 1.5 mm (1/16 in) long and tipped with a pappus of tawny hairs. Flowers from July to September.

Habitat: White snakeroot is native throughout southern Ontario in rich woods, thickets, clearings, waste places, ditches, meadows and beside lakes and streams, chiefly in basic soils.

Caution: The plant is poisonous to livestock and causes "milk-sickness" in humans via consumption of milk from affected animals.

Similar Species: It is distinguished by the combination of opposite, petiolate leaves with coarsely serrate margins and flat-topped inflorescences of small, white flower heads.

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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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