Plant · GBIF taxon 5400552
white snakeroot
Ageratina altissimaAlso known as Richweed, White Sanicle, Tall Boneset
White snakeroot forms bushy clumps in shady eastern North American forests, bursting into fluffy clusters of bright white flowers during late summer and autumn. Historically notorious for causing deadly milk sickness, all parts of the plant harbor the potent metabolic toxin tremetol, which passes into the milk of grazing cows. The plant serves as an important late-season nectar source for specialized native bees, butterflies, and moths.
ToxicPerennialWildflower
1 / 7—observations
—countries
—peak records
Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Diet & prey
- Sunlight
- Water
- Soil Nutrients
Predators
- Leaf-mining Flies
- Specialist Caterpillars
- Herbivorous Beetles
ThreatsHabitat destruction, invasive plant competition
HabitatsRich woodlands, moist thickets, shaded road verges, forest edges
Life spanPerennial (5 to 10+ years)
Size / weightNot available
Classification
- OrderAsterales
- FamilyAsteraceae
- GenusAgeratina
- SpeciesAgeratina altissima
Range data is not available yet.
Interaction riskHigh
- Low
- Moderate
- High
- Very high
- Why interaction risk is high
- Contains tremetol, a deadly metabolic toxin; never ingest any part or allow livestock to graze near it.
- Why it is dangerous
- Harbors tremetol, a potent cumulative toxin causing severe metabolic damage, tremors, organ failure, and historically fatal milk sickness.
- How to recognize a risky encounter
- Features broad opposite leaves with coarse teeth and dense, branched heads of tiny white disk flowers blooming late in the season.
- What to do
- Avoid handling without gloves if pulling plants, and clear it entirely from livestock pastures.
Responsible observation
- Identification: Look for opposite, distinctly stalked, dark green leaves with coarsely serrated margins beneath white flower clusters.
- Pasture Safety: Inspect livestock grazing areas in late summer to remove plants before animals consume them.
- Pollinator Watching: Observe the white blooms in autumn from a comfortable distance to spot visiting butterflies and native bees.
Close Relative (c) Thomas Koffel, some rights reserved (CC BY), uploaded by Thomas Koffel · cc-by
Close Relative (c) Michael J. Papay, some rights reserved (CC BY), uploaded by Michael J. Papay · cc-by
Close Relative (c) Douglas Goldman, some rights reserved (CC BY-SA), uploaded by Douglas Goldman · cc-by-sa
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