Hollow Joe-Pye-Weed (*Eutrochium fistulosum*)
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###### [](https://upload.wikimedia.org/wikipedia/commons/a/a7/Eutrochium_fistulosum%2C_Robin_Hill_Park%2C_2024-08-01-3.jpg) Photographed August 1.
Formerly *Eupatorium fistulosum,* but the genus *Eupatorium* has been split into several genera. This beautiful and elegantly constructed plant, also known as Trumpetweed, bears domes (the *dome shape* is a useful distinguishing feature) of dusty mauve flower heads on towers of whorled leaves, usually five to seven in a whorl. The plants can easily grow to seven feet or more. They prefer a damp environment, and are often seen in the soggier parts of roadsides and fields.
[](https://upload.wikimedia.org/wikipedia/commons/e/ea/Eutrochium_fistulosum%2C_Robin_Hill_Park%2C_2024-08-01-1.jpg)
These plants were growing in the native-plant field in Robin Hill Park, Moon Township.
[](https://upload.wikimedia.org/wikipedia/commons/d/d7/Eutrochium_fistulosum%2C_Robin_Hill_Park%2C_2024-08-01-2.jpg)
[](https://upload.wikimedia.org/wikipedia/commons/1/18/Eutrochium_fistulosum%2C_Robin_Hill_Park%2C_2024-08-01.jpg)
Gray describes the genus and the species.
EUPATORIUM. Thoroughwort. Heads discoid, 3-many-flowered; flowers perfect. Involucre cylindrical or campanulate, of more than 4 phyllaries. Receptacle flat or conical, naked. Corolla 5-toothed. Achenes 5-angled; pappus a single row of slender capillary barely roughish bristles. — Perennial (sometimes annual) herbs or shrubs, chiefly of trop. and temp. Am. (few in Eurasia and Afr.), often sprinkled with bitter resinous dots, with generally corymbose heads of white, bluish or purple flowers appearing near the close of summer. (Dedicated to *Mithridates Eupator,* 132-63 B.C., who is said to have used a species of the genus in medicine.)
*E. fistulòsum* Barratt (tubular). Joe-Pye-weed, Trumpet-weed. — *Stems strongly glaucous* (when fresh), suffused with purple, *unspotted or rarely spotted,* glabrous, *hollow;* leaves in 4's-7's, narrowly to broadly *lanceolate,* attenuate to base and apex, *regularly crenate or crenate-serrate,* sparingly fine-pubescent to glabrous beneath, pinnately veined; *corymb round-topped or doming,* when fully developed hemispherical to thick-subcylindric, up to 1-5 dm. high and 1-3 dm. broad, the lower branches divergent; *heads purple or lilac-pink,* 5-8-flowered; *corolla 3.5-4.8 mm. long, barely or not at all exserted;* achenes 3.2-4.5 mm. long. (*E. purpureum* in part of ed. 7, not L.) — Damp thickets, meadows, etc., Fla. to e. Tex., n. to sw. Me., sw. Que., N.Y., O., Ind., 111., la. and Okla. Mid-July-Sept.