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Wisconsin Plant of the Week

Eupatorium rugosum Houtt.

Asteraceae (Aster or Sunflower Family)

Common Name:

white snakeroot


White snakeroot is a native perennial that grows in partial shade in most deciduous woodlands from dry to moist sites. It spreads easily by seed and short rhizomes with fibrous roots and tends to be weedy along trails, the woods edge or following some disturbance.

The plants are usually single stems, up to 1 m tall. Branching occurs only just below the inflorescence, which is more or less flat-topped. Leaves are opposite, smooth and thin with 3 prominent veins and evenly toothed margins.  Leaf shape is rounded at the base and pointed at the tip.  Leaves have a distinct stalk or petiole.

The bright white flowers bloom from late August until frost. They’re arranged in dense heads -- like all the flowers in the Aster Family.  Unlike the asters or sunflowers, the genus Eupatorium has only tiny disc flowers and no showy ray flowers. 

The flowers of white snakeroot are very similar to those of boneset (E. perfoliatum), which grows in wetter sites.  Boneset has hairy leaves that surround the stem and have no petiole.

Tremerol, an alcohol in the leaves of white snakeroot, is fat soluble and accumulates in grazing cattle and horses causing a fatal disease. Humans contract the disease by drinking contaminated milk. After getting “milk sickness”, 19th century pioneers often abandoned their land, assuming the disease was related to poor soil.  Moving on, they cleared new land to pasture, where within a few years white snakeroot followed. The disease reached epidemic proportions before it was understood.

  • Origin of the name: Eupatorium, eupatorion, Gk., name for another (unrelated) species; rugosusm, L., wrinkled.
  • Range:  NS to Sask., s. to GA, TX
  • WI Range:  Throughout WI except extreme northwest
  • Common associates: sugar maple, wild geranium, enchanter’s nightshade
  • Wetland Indicator Status: FACU
  • Coefficient of Conservatism: C = 4 (S&W), C = 4 (MI)
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