The genus Eupatorium Linnaeus
and Eupatorium perfoliatum Linnaeus
The words or terms in red
(actually dark orange) in the text are defined in a
The genus Eupatorium Linnaeus
Species of the
genus Eupatorium are mostly
herbaceous perennials that are between 30 cm
and 2 m high. A few are shrubs.
Their stems are erect and usually not branched.
Their leaves are mostly cauline, usually
Their flower heads
are discoid, in
corymbiform arrays. They have
persistent phyllaries in two or more series.
They from a few to over 15 florets with a
usually white corolla.
The cypselae are brownish to black and have
a persistent pappus of whitish
The plant grows from a thick
They have 10 chromosomes.
Species of Eupatorium, although poisonous, have been used in folk
medicine, for instance to excrete excess uric acid which causes gout. However,
Eupatorium is said to have many beneficial uses, including treatment of
dengue fever, arthritis, infectious diseases, migraines, worms, malaria, and
Eupatorium species are used as food plants by the larvae of some
Lepidoptera species including Bucculatrix
eupatoriella (which feeds exclusively on Eupatorium perfoliatum).
The genus consists of over 40 species, 24 of which,
including 2 hybrids, are found in
North America; many species are also found in Europe and eastern Asia.
Only one species, Eupatorium perfoliatum, is found in Québec.
The genus belongs to the
Eupatorium perfoliatum Linnaeus
Eupatorium perfoliatum is a perennial herb, with an erect stout,
cylindrical hairy stem, from 2 to 4 feet high, and branched at the top.
It is common to the Eastern United States and Canada.
The terminal flower clusters are white and reminiscent of
Achillea millefolium (Yarrow).
The stems appear to be growing through the middle of the
The root system is fibrous and produces rhizomes in abundance,
the plant typically forming vegetative colonies.
The species shows considerable variety in size, hairiness, form of leaves and
The odor of the plant is slightly aromatic,
the taste astringent and strongly bitter.
Some botanists split the species in two
The chromosome number of the species
(2n) is 20.
- Eupatorium perfoliatum L. var. colpophilum Fern. & Grisc.
- Eupatorium perfoliatum L. var. perfoliatum
The genus name refers to Mithridates VI, 132-63 BC, also known as
Mithridates the Great and Eupator Dionysius; he was king of Pontus in northern
Anatolia from 120 to 63 BC. He is remembered as one of Rome's most formidable
and successful enemies who engaged three of the most prominent generals of the
late Roman Republic: Sulla, Lucullus, and Pompey the Great.
Mithridates is most famously said to have sought to harden himself against
poison, both by taking increasing sub-lethal doses of the poisons to build
tolerance, and by fashioning a universal antidote, using among other things
Eupatorium species, to protect him from all earthly poisons.
In Latin, per means through,
and foliatus means well-stocked in leaves
so that the
epithet refers to the stem of the plant
that appear to be growing through the middle of the leaves.
Some of the vernacular names of
Eupatorium perfoliatum are
Thoroughwort, Thoroughwax, Agueweed, Crosswort, Eupatorium, Feverwort,
Gravelroot, Indian Sage, Sweating Plant, Teasel and Boneset,
the last one being the most common.
The French vernacular name is Eupatoire perfoliée.
Eupatorium perfoliatum has also been known as:
- Eupatorium chapmanii Small
- Eupatorium perfoliatum var. colophilum Fernald & Griscom
- Eupatorium perfoliatum var. cuneatum Engelmann
Eupatorium perfoliatum is quite distinctive, with its
perfoliate leaf bases,
its large size and large and flat arrays of white flower heads.
Its leaves serve in fact to distinguish the species at the first glance -
they may be considered either as perforated by the stem,
(hence the specific name), or as consisting of two opposite leaves joined at
the base, hence as connate.
- Single, sparsely branched.
- Puberulent throughout.
- Usually opposite, perfoliate
- With blades pinnately nerved.
- Oblong and tapering toward
- 5 to 15 cm long and 1.4 to 4 cm wide.
- With serrate margins.
- Downy and resinous and dotted
- In terminal arrays.
- With 7 to 10 phyllaries in
one or two series.
- Without ray florets.
- With about 10 tubular florets
with a whitish corolla with 5
- With a villous to densely
- With 5 stamens.
- With a long divided style.
- About 1/6 to 1/4 inch across.
- Blooming from August to September in my area, 25 km north of Montréal.
- A cypsela about 1/10 inch long.
- With a pappus about 3 mm long of
20 to bristles.
Eupatorium perfoliatum is common and familiar plant in low meadows,
swamps, wet prairies, open woods, around ponds and lakes, in sloughs, along
streams; it doesn't stray far from wetland areas of one kind or another. It
is a plant of sunny areas.
Eupatorium perfoliatum is a plant of the eastern United States
and Canada, with a range from Nova Scotia to Florida, as well as from Louisiana
and Texas through North Dakota. The map shows the USA states and Canadian
provinces where the plant can be found.
Eupatorium perfoliatum is said to be a stimulant,
laxative, acting slowly and persistently,
and its greatest power is manifested upon the stomach, liver, bowels and uterus.
Eupatorium perfoliatum was a favorite medicine of the North American
Indians. The Abenaki used it to mend bones, the Cherokee as a purgative, as a
sudorific or as infusion taken for colds. The Chippewa used the roots
to correct irregular menses.
Eupatorium perfoliatum has always been a popular remedy in the United
States. It is said to be the best remedy for the relief of the symptoms that
accompany influenza, particularly muscle pain.
Recent research indicates that the
sesquiterpene lactones and the
flavones in the plant
(especially eupatorin) may have anti-cancer activity.
Chinese medicine uses Eupatorium perfoliatum for summer colds,
heatstroke, tightness of the chest, and bad breath.
In homeopathy it is prescribed for flu and malaria.
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 of the picture on the right 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.