Fauna
Plant · GBIF taxon 5400552

White Snakeroot

Ageratina altissima

Also known as Richweed, White Sanicle

White snakeroot blooms in late summer and autumn, blanketing shaded eastern forests and woodland edges with dense clusters of fluffy, snow-white flower heads. Its sharply toothed, heart-shaped leaves contain tremetol, a dangerous toxin that historical grazing cattle passed into milk supplies, causing fatal milk sickness in early settlement communities. Today, these native perennials serve as vital late-season pollen sources for native bees and butterflies seeking nectar before winter.

ToxicWildflowerFall Bloomer
White Snakeroot reference1 / 7
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Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Key facts
Diet & prey
  • Autotrophic
Predators
  • Leaf-miner flies
  • Aphids
  • Specialist beetles
ThreatsLand development, invasive plant competition
HabitatsRich woods, forest borders, thickets, shaded pastures
Life spanPerennial (5–10+ years)
Classification
  1. OrderAsterales
  2. FamilyAsteraceae
  3. GenusAgeratina
  4. SpeciesAgeratina altissima
Range & activity
Range data is not available yet.
Safe observation
Interaction riskHigh
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is high
Contains toxic tremetol, causing severe poisoning if ingested; keep livestock away and do not consume.
Why it is dangerous
Contains the toxin tremetol, which causes severe trembling, liver damage, and fatal milk sickness if consumed directly or through animal milk.
How to recognize a risky encounter
Recognize its flat-topped fuzzy white flower heads and opposite, heart-shaped, coarsely toothed leaves in shaded woods.
What to do
Never ingest any part of the plant and keep livestock from grazing in pastures containing established stands.
Responsible observation
  • Identification: Look for bright white flower clusters topping opposite, coarsely toothed, heart-shaped leaves.
  • Safety: Avoid harvesting or allowing livestock to graze near dense patches due to tremetol toxicity.
  • Wildlife Watching: Observe late-season pollinators visiting the flowers on warm autumn afternoons.
Related species
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