The Ageratina Spach genus and Ageratina altissima (L.) King & H. E. Robins

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.

The genus Ageratina Spach

Ageratina is a genus of annual to perennial herbs or shrubs of eastern United States and Canada and of Central and South America. It is constituted by over 200 species. A single species is found in Québec, Ageratina altissima of the variety altissima. The other variety of the species, Ageratina altissima var roanensis is found in the south-east of the USA. Some species of this genus are used in the folk medicine due to their tonic, febrifuge, emmenagogue, diaphoretic and anti-syphilitic properties.

The leaves of the species are cauline opposite, toothed and petiolate. Their inflorescences are terminal, with flower heads in dense panicles; their phyllaries are herbaceous, hardly imbricate, in one or tow series. They do not have ray florets. The disc florets are numerous, bisexual, tubular. The fruits are slender achenes, 5-angled, with a fragile pappus that falls off easily.

The genus belongs to the Asteraceae family. Its is found in North and South America and in Australia. aug_26_06.gthmb can't be loaded.

Ageratina altissima (L.) King & H. E. Robins

Ageratina altissima was previously usually known as Eupatorium rugosum; in fact, on August 25th 2007, google returned 34,500 results for Eupatorium rugosum vs. 10,800 for Ageratina altissima. Ageratina altissima is native to eastern North America. The taxon found in Québec is Ageratina altissima var. altissima. Ageratina altissima is a branched perennial herb usually about 3 feet tall but varying from 1 to 5 feet. In late summer, numerous small heads of minute white flowers appear at the top of the stem and the ends of the branches. These flower heads, except that they are white, are almost exactly like the flower heads of the familiar Ageratum of gardens (hence the genus name). Later the flowers are replaced in the heads by small black seeds each with a crown of soft white hairs.


Ageratina is the diminutive of Ageratum. In Greek, αγηρατον (agêraton) is the name of the Sweet Marjoram or of the Oregano and is referred to by Dioscoride, in his De materia medica, 4, 58. Since some species of the Ageratum might look somewhat like one of these two plants, the name was given to the genus.

In Latin, altus mean high, altissimus is its superlative, and altissima the feminine of this superlative. The epithet refers then to the size of Ageratina altissima which is much higher than many other Ageratina species. Ageratina is a diminutive, altissima is a superlative; joining both does looks like an oxymoron !

Common names

Two of the vernacular names of Ageratina altissima are White Snakeroot and White Sanicle. The first common name of this species derives from the erroneous belief among early American settlers that the bitter rhizomes were beneficial in the treatment of snakebites; they are in fact highly toxic. The French vernacular name is Eupatoire rugueuse referring still to the old genus name.


Ageratina altissima var. altissima has also been known as:


Ageratina altissima is easy to identify by its large size, its white distinctive flower heads, its somewhat large and opposite leaves, and by its habitat, shaded woods.

Because its leaves resemble those of some species of the Urticaceae family (the nettle family) and of some other plants with similar leaves, they are often mistaken for it; but a rapid inspection should quickly show the differences.



The root system consists of spreading rhizomes and shallow fibrous roots.


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Flower heads



Ageratina altissima is found in rich, rocky woods, at the base of wooded bluffs, in rock outcrops, in thickets. It may persist after clearing, and often may be found many years after the land has been cleared, although usually in such areas it occurs only as scattered unthrifty plants.


map_na.jpg can't be loaded. Ageratina altissima is somewhat common in eastern North America. In Canada, it is found in New Brunswick, Nova Scotia, Ontario, Québec, Manitoba and Saskatchewan. The map shows the US States and Canadian provinces where the plant can be found.


Ageratina altissima is very toxic if eaten in quantity as it contains barium sulphate. Cows which graze on the plant produce poisonous milk and this was the cause of death for a number of pioneers in the USA. The toxic agent is tremetone. Large losses of human life occurred in the 19th century from the mysterious milk sickness. Mortality ranged from 10 to 25 %, and the population of entire villages left a location because they could not find the cause of the disease. It was later discovered that cattle had ingested Ageratina altissima and that a toxin was subsequently passed through the milk to humans and was toxic.

Several types of herbivorous livestock have also been poisoned by ingesting Ageratina altissima, resulting in a disease called trembles. Cattle, goats, horses, sheep, and swine have shown toxic reactions. Suckling animals can develop milk sickness as well. Trembles was more of a problem in the past, before the increased use of herbicides and prepared feeds. Poisoning was also more frequent when animals were allowed to range through bushlots.

American Indians used a tea made from the roots to help diarrhea, painful urination, fevers, and kidney stones. The plant was also burned and the smoke used to revive unconscious patients.


The photos of the gallery were taken either with one of the following: The title in the window shows the date when the picture was taken, i.e. jan_30_06... would mean that the photo was taken on the 30th of January, the 06 is for the 6th picture taken that day.

The month, day and picture number might be followed by a letter:

Click on the thumbnails to get larger view. The original photos are usually in TIFF format, the photos shown are generally in JPEG format, usually of dimensions one half (surface one quarter) for loading time reduction.


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Flower heads

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