Eutrochium maculatum (Linnaeus) Sida
The words or terms in red
(actually dark orange) in the text are defined in a
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
The species consists of three
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.
- Eutrochium maculatum var. foliosum
- Eutrochium maculatum var. maculatum
- Eutrochium maculatum var. bruneri
The species belongs to the
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).
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:
- Eupatorium maculatum L.
- Eupatorium purpureum L. var. maculatum
- Eupatorium bruneri A. Gray
- Eupatoriadelphus maculatus (L.) R. M. King & H. Rob. var.
bruneri (A. Gray) R. M. King
- Eupatoriadelphus maculatus (L.) R. M. King & H. Rob
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.
Eutrochium maculatum has fibrous roots and spreading
rhizomes that can produce dense stands.
- Purple or spotted with purple.
- Erect, ridged, and usually unbranched.
- Those positioned on the upper portion of the stem near the base of the
flower heads are typically
- Those borne on the remainder of the stem are
whorled with usually 4 to 5 leaves
- Between 2 and 8 inches long.
- Broadly ovate
or lanceolate and
- With margins with teeth
that vary from sharp and serrate
to shallow and rounded.
- Arranged in flat-topped terminal
up to 7 inches wide.
- About 1/3 inch wide.
- Without ray florets.
- With between 8 and 22
- With oblong round-tipped
- With 5 stamens.
- Blooming from the beginning of August to the beginning of September
in may area, 25 km north of Montréal.
- Dark brown, narrow achenes;
- With a small pappus.
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.
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.
- 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 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.