The Ageratina Spach genus and Ageratina altissima
(L.) King & H. E. Robins
The words or terms in red
(actually dark orange) in the text are defined in a
The genus Ageratina Spach
Ageratina is a genus of
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
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,
diaphoretic and anti-syphilitic properties.
The leaves of the species are
opposite, toothed and
Their inflorescences are
terminal, with flower heads in dense
their phyllaries are
herbaceous, hardly imbricate, in one or tow
series. They do not have ray florets.
The disc florets are numerous,
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.
Ageratina altissima (L.) King & H. E. Robins
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 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 is a diminutive, altissima is a superlative;
joining both does looks like an oxymoron !
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:
- Ageratum altissimum L., non Eupatorium altissimum L.
- Eupatorium rugosum Houtt.
- Eupatorium rugosum Houtt. var. chlorolepis Fern.
- Eupatorium rugosum Houtt. var. tomentellum
(B. L. Robins.) Blake
- Eupatorium rugosum Houtt. var. villicaule (Fern.) Blake
- Eupatorium urticifolium Reichard var. tomentellum B. L.
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,
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
The root system consists of spreading
rhizomes and shallow
- Up to 3 feet tall, erect, herbaceous.
- single or multiple from base.
- Glabrous to densely
- With a petiole up to 4 cm long.
- Up to 5 inches long by 3 inches wide.
- With 3 main veins that show prominently on the underside.
- Dull deep green abaxially,
light green adaxially.
- In a terminal corymbose arrangement.
- With a pubescent peduncle up to 1 cm
- Up to 5 mm long and from 2 to 4 mm in diameter.
- With a single serie of phyllaries
that are only slightly overlapping, that are
linear-oblong to linear,
pubescent, about 5mm long and 1mm broad.
- Without ray florets.
- With up to a dozen disk florets
per flower head.
- With the flower corollas white,
with 5 acute lobes, with 5
stamens and white
filaments; with whitish to pale
- Pollinated by bees, wasps, various
flies, butterflies, and moths.
- Blooming from the middle of August to the middle of September in my
area, 25 km north of Montréal.
- A greenish achene in flower,
black when ripe.
- With a pappus 3 to 4 mm long.
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.
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
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.
- Minolta DiMAGE 7.
- Canon PowerShot A530
- Canon Xt Rebel, usually with the EF-S60mm f/2.8 Macro USM objective.
- EPSON Perfection 1650 (scanner).
The month, day and picture number might be followed by a letter:
- c for the Canon Xt Rebel.
- a for the Canon A530.
- m for the Minolta DiMAGE 7.
- s for the EPSON scanner.
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.
The leaves on the left were scanned at 300 dpi,
and the dimensions of the resulting picture divided by 2 (area divided by 4);
this allows to measure the dimensions of the leaves.