The genus Eupatorium Linnaeus and Eupatorium perfoliatum Linnaeus

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

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 opposite. Their flower heads are discoid, in paniculiform or 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 bristles. The plant grows from a thick rhizome. 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 diarrhea.

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 Asteraceae family.

Eupatorium perfoliatum Linnaeus

aug_08_15.gthmb can't be loaded. 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 perfoliated leaves. 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 inflorescence. The odor of the plant is slightly aromatic, the taste astringent and strongly bitter. Some botanists split the species in two varieties: The chromosome number of the species (2n) is 20.


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.

Common names

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 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, perfoliate (hence the specific name), or as consisting of two opposite leaves joined at the base, hence as connate.

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Flower heads



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. map_na.jpg can't be loaded.


Eupatorium perfoliatum is said to be a stimulant, diaphoretic, emetic, antispasmodic, cathartic, febrifuge and 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.

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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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.

Flower heads

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