Ageratina altissima

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Ageratina altissima
Ager alti.jpg
Photo by John R. Gwaltney, Southeastern
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta - Flowering plants
Class: Magnoliopsida - Dicotyledons
Order: Asterales
Family: Asteraceae ⁄ Compositae
Genus: Ageratina
Species: A. altissima
Binomial name
Ageratina altissima
(L.) King & H. Rob.
AGER ALTI dist.jpg
Natural range of Ageratina altissima from USDA NRCS Plants Database.

Common names: snakeroot; white snakeroot, common white snakeroot, common milk-poison

Taxonomic notes

Synonyms: Eupatorium rugosum Houttuyn; E. urticifolium Reichard[1]

Varieties: Ageratina altissima var. angustata (A. Gray) Blake; Eupatorium rugosum var. chlorolepsis Fernald; E. rugosum var. tomentellum (B.L. Robinson) Blake[1]


A description of Ageratina altissima is provided in The Flora of North America. It is a perennial.[2]


It is common in north Florida. Found west to Texas and north to Canada.[2]


Ageratina altissima competes by allelopathy. Aqueous extracts from roots and especially shoots decreases the rate of germination, percentage of germination, and size of germinated Lettuce and Radish seeds in Petri dishes as well as in pots of forest soil.[3]


In the Coastal Plain, Ageratina altissima grows in shady to partially shady areas,[4] preferring wet or moist soils, including sandy alluvial soil, drying sandy loam, and wet loamy soil with limestone outcrops.[5]

The plant is common in the eastern deciduous forest herb layer.[3] This species also occupies scrubs, thickets, floodplain forests, and slope/bluff habitats.[4] It can also be found in disturbed areas like roadsides, old fields, clearings, and the margins of waterways.[5]

Associated species include beech, hickory, magnolia, sweetgum, pine, Taxodium, Nyssa, Acer, Fraxinus, Quercus, Eupatorium perfoliatum, and others.[4]


In the Coastal Plain, Ageratina altissima flowers and fruits between late summer to fall,[6][3] with peak inflorescence in September, October, and November.[4][7]

Seed dispersal

A. altissima disseminates its mature seeds (achenes) by wind in fall and winter. Each plant can produce thousands of seeds at a time. [8]

Seed bank and germination

Ageratina altissima usually needs light to germinate. It exhibits a Type II response to stratification: Germination in the spring generally can occur at a lower temperature than germination in the fall as a result of dormancy loss in the winter. Thus, germination in the spring is more likely because of relatively higher temperatures and lower temperature requirements than in fall.[5]

Fire ecology

A. altissima resprouts following fire. It is most abundant after a late-season (early October) burn.[9]


Ageratina altissima has been observed to be visited by sweat bees from the family Halictidae such as Agapostemon sericeus and Augochlorella persimilis, as well as flies from the families Chloropidae and Calliphoridae.[10]

Herbivory and toxicology

This species is known to host ladybugs including Coccinella septempunctata (family Coccinellidae).[11] Otherwise, A. altissima is mostly avoided by many insects.[3] This species contains tremetol, a complex alcohol and glycoside that can cause a fatal disease known as staggers in cattle. The toxin is capable of being passed through milk and can cause fatalities in humans who consume infected milk.[12]

Diseases and parasites

Leaf miners and flea beetles may attack the foliage.[13]

Conservation, cultivation, and restoration

Cultural use

Native Americans have reportedly used a decoction of the roots as a remedy for snake bites.[13]

Photo Gallery

References and notes

  1. 1.0 1.1 Weakley, A.S. 2020. Flora of the Southeastern United States. Edition of 20 October 2020. University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
  2. 2.0 2.1 Hall, David W. Illustrated Plants of Florida and the Coastal Plain: based on the collections of Leland and Lucy Baltzell. 1993. A Maupin House Book. Gainesville. 100. Print.
  3. 3.0 3.1 3.2 3.3 Corbett, B. F. and J. A. Morrison (2012). "The allelopathic potentials of the non-native invasive plant Microstegium vimineum and the native Ageratina altissima: two dominant species of the eastern forest herb layer." Northeastern Naturalist 19: 297-312.
  4. 4.0 4.1 4.2 4.3 Florida State University Robert K. Godfrey Herbarium database. URL: Last accessed: June 2014. Collectors: Loran C. Anderson, Robert K. Godfrey, P. L. Redfearn, Jr., Richard S. Mitchell, Patricia Elliot, Robert L. Lazor, John B. Nelson, A. Gholson Jr., Angela M. Reid, and K. M. Robertson. States and Counties: Florida: Leon, Jefferson, Jackson, Gadsden, Liberty, and Calhoun. South Carolina: Greenville.
  5. 5.0 5.1 5.2 Walck, J. L., C. C. Baskin, et al. (1997). "Comparative achene germination requirements of the rockhouse endemic Ageratina luciae-brauniae and its widespread close relative A. altissima (Asteraceae)." American Midland Naturalist 137: 1-12.
  6. Wunderlin, Richard P. and Bruce F. Hansen. Guide to the Vascular Plants of Florida. Second edition. 2003. University Press of Florida: Gainesville/Tallahassee/Tampa/Boca Raton/Pensacola/Orlando/Miami/Jacksonville/Ft. Myers. 295. Print.
  7. Nelson, G. PanFlora: Plant data for the eastern United States with emphasis on the Southeastern Coastal Plains, Florida, and the Florida Panhandle. Accessed:15 JAN 2015
  8. Lau, J. M. and D. L. Robinson (2010). "Phenotypic selection for seed dormancy in white snakeroot (Eupatorium rugosum)." Weed Biology & Management 10: 241-248.
  9. Pavlovic, N. B., S. A. Leicht-Young, et al. (2011). "Short-term effects of burn season on flowering phenology of savanna plants." Plant Ecology 212: 611-625.
  10. [1]
  11. [2]
  12. [[3]]Accessed:March 22, 2016
  13. 13.0 13.1 [[4]]Missouri Botanical Gardens. Accessed: March 22, 2016