Eutrochium maculatum (Linnaeus) Sida

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

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Eutrochium maculatum was previously mainly known as Eupatorium maculatum. In fact, on the 5th of September 2007, google returned 54 500 results for Eupatorium maculatum vs. only 152 for Eutrochium maculatum. The species is native to North America. It is a coarse, clumping, erect perennial with a whorled leaf arrangement bearing 3 to 6 lanceolate leaves at each node. It can reach 4 to 6 feet in height. It has the widest geographic distribution and greatest morphologic variability among species in the genus. The species consists of three varieties:

The first two varieties are found in the eastern half of the USA and Canada, both are found in Québec; the last one is mostly found west of the Mississippi River and, in Canada, from Ontario to British Columbia. Their chromosome number (2n) is 20.

The species belongs to the Asteraceae family.


In Greek, ευ (eu) means well and τροχο (trokho) means wheel, the genus name alluding to the usually whorled leaves of the species, a bit as the rays of a wheel. The previous genus name, Eupatorium, referred to Mithridates Eupator, King of Pontus about 115 BC who is said to have discovered an antidote to a commonly used poison in one of the species.

In Latin, maculatus is the past participle of the verb maculare that means to speck, to fleck. The epithet refers to the plants having their stem purple-speckled (but sometimes uniformly purple).

Common names

Two of the vernacular names of Eutrochium maculatum are Joe Pye Weed and Mottled Joe Pye Weed.

The vernacular French names are Eupatoire maculée for the maculatum variety and Eupatoire feuillue for the foliosum variety, referring still to the old name of the genus.


Eutrochium maculatum has also been known as:


Eutrochium maculatum is easy to identify with its whorl of elongate leaves and its flower heads of many very small purple flowers. The two varieties found in Québec are differentiated by their first whorls of leaves subtending the flower heads; if it equals or surpasses the arrays of the flower heads, the variety is foliosum, else, if the first whorls of leaves subtending the flower heads is smaller than the arrays of the flower heads, the variety is maculatum. draw.jpg can't be loaded.


Eutrochium maculatum has fibrous roots and spreading rhizomes that can produce dense stands.



Flower heads



Eutrochium maculatum grows in full sun in damp areas, on ditchbanks, wild marshes, along the edges of bogs or occasionally on the bog, and in a variety of other wetland habitats. It thrives in moist calcareous soils.


Eutrochium maculatum is found in eastern North America. The map on the left shows the distribution in North America of Eutrochium maculatum var. foliosum and the map on the right shows the distribution of Eutrochium maculatum var. maculatum.

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Eutrochium maculatum was used by the Algonquin of Québec for menstrual disorders and to facilitate the recovery of women after childbirth. The Cherokee used the roots to cure rheumatism and as a diuretic while the Chippewa used them as a wash for joint inflammations.


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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