Ageratina altissima

white snakeroot


Leaf Arrangement


Leaf Margin


Leaf Type


Leaf Shape

deltoid, ovate

Growth Form


Flower Color


Flower Month

August - November

Height (meters)

0.3 - 1.2

Milky Sap








Growing Season

Warm season

Wetland Class


Prairie Coefficient of Conservatism


Field Characters

Similar to Eupatorium serotinum which occurs on similar sites but has a 1 inch petiole, longer that that of Ageratina altissima. Eupatorium serotinum also has 11 flowers per head, phyllaries in 3 or more series, and resinous glands, while A. altissima has 20 flowers per head, phyllaries in 2 series and it has no glands.

Cultural Information

Control includes management for vigorous perennial prairie species.

Animal Use

Poisonous to livestock. It contains the poison "tremetol" that is an unsaturated alcohol. It occurs mostly in the green tissues and decreases as plants dry. Tremetol is not easily excreted by animals (except in milk), so it has a cumulative effect. Cattle, horses, sheep, and goats are susceptible. When excreted in milk it causes "milk sickness" in humans. Symptoms in animals are weight loss, trembling, depression, inactivity, labored respiration, constipation, nausea, weakness, and finally, inability to stand. Death may occur in a few to several days. Persons with milk sickness become constipated, vomit frequently, and are delirious. Laxatives improve an animal's chances. Bees (long-tongued) Apidae (Apinae): Apis mellifera sn cp fq (Rb, Gr); Apidae (Bombini): Bombus griseocallis sn (Gr), Bombus vagans sn cp (Gr); Anthophoridae (Ceratinini): Ceratina dupla dupla sn (Gr); Megachilidae (Megachilini): Megachile centuncularis sn cp (Gr), Megachile latimanus sn cp (Rb, Gr), Megachile mendica sn cp (Rb, Gr) Bees (short-tongued) Halictidae (Halictinae): Agapostemon sericea sn (Gr), Augochlorella striata sn, Halictus (or Lasioglossum) sp. sn cp (Gr), Halictus confusus sn cp (Rb, Gr), Halictus ligatus sn cp fq, Lasioglossum coriaceus sn (Gr), Lasioglossum imitatus sn, Lasioglossum versatus sn cp (Gr), Lasioglossum zephyrus sn cp (Gr); Colletidae (Colletinae): Colletes compactus sn (Gr) Wasps Sphecidae (Larrinae): Ancistromma distincta; Sphecidae (Sphecinae): Sphex ichneumonea (Gr); Scoliidae: Scolia bicincta (Rb, Gr); Vespidae: Dolichovespula maculata, Vespula germanica; Vespidae (Eumeninae): Ancistrocerus adiabatus (Rb, Gr) Flies Culicidae: Aedes vexans (Gr); Scathophagidae: Scathophaga furcata (Gr); Syrphidae: Allograpta obliqua (Rb, Gr), Eristalis arbustorum (Gr), Eristalis brousii (Gr), Eristalis dimidiatus (Gr), Eristalis tenax (Gr), Eristalis transversus (Gr), Helophilus fasciatus (Gr), Paragus tibialis (Gr), Rhingia nasica, Spilomyia fusca (Gr), Spilomyia longicornis (Rb, Gr), Syritta pipiens (Gr), Syrphus ribesii (Rb, Gr), Toxomerus geminatus (Gr), Tropidia quadrata (Gr); Bombyliidae: Anthrax oedipus (Gr), Exoprosopa fasciata, Sparnopolius confusus (Gr); Tachinidae: Archytas analis (Gr), Estheria abdominalis, Gymnoclytia immaculata (Gr), Gymnoclytia occidua, Gymnosoma fuliginosum (Gr), Paradidyma singularis Phyllomya cremides (Gr); Anthomyiidae: Delia platura (Gr); Calliphoridae: Lucilia caesar (Gr), Lucilia sericata (Gr); Muscidae: Graphomya maculata (Gr), Musca domestica (Gr), Neomyia cornicina, Stomoxys calcitrans (Gr) Butterflies Nymphalidae: Limenitis archippus (Gr), Phyciodes tharos (Gr), Speyeria aphrodite aphrodite (Gr); Lycaenidae: Celastrina argiolus Skippers Hesperiidae: Ancyloxypha numitor (Gr) Moths Ctenuchidae: Cisseps fulvicollis; Noctuidae: Anagrapha falcifera (Gr); Tortricidae: Grapholita interstinctana (Gr) Beetles Chrysomelidae: Acalymma vittata (Gr), Epitrix cucumeris (Gr); Curculionidae: Hypera punctata (Gr) Plant Bugs Miridae: Lygus pratensis (Gr), Plagiognathus sp. (Gr)

Natural History

The Acadians of south Louisiana call it "tete de vieille femmes", meaning "heads of the old women". This apparently refers to the clusters of white flowers (Homes 1990).


Moist to slightly dry deciduous woodlands, woodland borders, thickets, partially shaded to shady seeps, bluffs, woodland meadows along rivers, powerline clearances in woodlands, shady corners of pastures and yards. This species is especially common in wooded areas that are rather disturbed and degraded, although it can also occur at higher quality sites.