Eutrochium fistulosum

{{Short description|Species of flowering plant}}

{{Use dmy dates|date=March 2023}}

{{Speciesbox

| image = Eupatoriumfistulosum.jpg

| image_caption = Eutrochium fistulosum with a butterfly

| genus = Eutrochium

| species = fistulosum

| authority = (Barratt) E.E.Lamont

| synonyms_ref = {{ThePlantList |id=gcc-88341 |taxon=Eutrochium fistulosum |authority=(Barratt) E.E.Lamont |access-date=12 May 2015}}{{Tropicos|50274912|Eutrochium fistulosum|(Barratt) E.E. Lamont}}

| synonyms =

• Eupatorium fistulosum Barratt
• Eupatoriadelphus fistulosus (Barratt) R.M. King & H. Rob.

}}

Eutrochium fistulosum (Eupatorium fistulosum), also called hollow Joe-Pye weed,{{GRIN | accessdate=9 June 2014}} trumpetweed, or purple thoroughwort, is a perennial North American flowering plant in the family Asteraceae. It is native to southern Canada and throughout the eastern and south central United States from Maine west to Ontario, Wisconsin, and Missouri and south as far as Florida and Texas.{{BONAP |genus=Eutrochium |species=fistulosum |date=2014}} The specific name fistulosum refers to the tubular stem; see fistula.

Eutrochium fistulosum is a herbaceous perennial plant sometimes as much as {{convert|350|cm|in ftin|abbr=on}} tall. It is found in moist, rich soil alongside ditches and marshes, or in wet forests. It flowers from mid-summer to the first frosts, makes an attractive backdrop in garden plots, and is very attractive to butterflies, bees, and other nectar-feeding insects.{{cite book| author-link=Neltje Blanchan | last=Blanchan | first=Neltje | title=Wild Flowers Worth Knowing | year=2005 | via=Project Gutenberg Literary Archive Foundation}}Tew, James [http://beelab.osu.edu/factsheets/sheets/2168.html Some Ohio Nectar and Pollen Producing Plants] {{Webarchive|url=https://web.archive.org/web/20061004224607/http://beelab.osu.edu/factsheets/sheets/2168.html |date=4 October 2006 }} Ohio State University Extension Factsheet In addition, it is a larval host to the Clymene moth, eupatorium borer moth, ruby tiger moth, and the three-lined flower moth.The Xerces Society (2016), Gardening for Butterflies: How You Can Attract and Protect Beautiful, Beneficial Insects, Timber Press.

The plant has one simple erect stem, which is green with purple dots or longitudinal dashes and can grow over six feet tall. The upper stems are reddish or purplish. Leaves and primary subdivisions of the flower head appear in whorls of 3–5 (rarely 2 or 6, the rotational symmetry of most plants is consistent). Leaves are large, long and sharply toothed. One plant can produce several flower heads in a branching array, each head with 4-7 pink or purple disc flowers but no ray flowers.{{eFloras|1|250066767|Eutrochium fistulosum |tribe=Eupatorieae |first= Eric E. |last=Lamont}}

File:JoePye-3fold.jpg|3-fold symmetry

File:JoePye-4fold.jpg|4-fold symmetry

File:JoePye-5fold.jpg|5-fold symmetry

File:JoePye-6fold.jpg|6-fold (uncommon)

File:JoePyeWeedStem.jpg|Stem sections