393. Eutrochium Rafinesque, New Fl. 4: 78. 1838.
Joepyeweed, eupatoire [Greek eu-, well, truly, and trocho-, wheel-like, alluding to whorled leaves]
Eric E. Lamont
Eupatoriadelphus R. M. King & H. Robinson; Eupatorium Linnaeus sect. Verticillatumde Candolle
Perennials, 30–350+ cm. Stems (sometimes ± purple, sometimes glaucous, internodes usually shorter than leaves) erect, unbranched. Leaves mostly cauline; mostly whorled (3–7 per node), rarely opposite; petiolate; blades pinnately veined or ± 3-nerved from at or near bases, deltate-ovate, lance-elliptic, lanceolate, lance-ovate, or ovate (bases gradually or abruptly tapered), margins serrate (usually with gland at apex of each tooth, apices acuminate), abaxial faces usually gland-dotted and hirsute, puberulent, pubescent, scabrous, or stipitate-glandular, sometimes glabrate, adaxial faces mostly puberulent to scabrous-hirsute and glabrescent, sometimes glabrate or glabrous. Heads discoid, in (flat-topped or convex to rounded) compound, corymbiform arrays. Involucres cylindric, 2.5–7 mm diam. Phyllaries persistent, 10–22 in 5–6 series, (pale pink to purple, rarely white, tightly appressed) striate or 1-nerved, mostly lance-ovate to lanceolate, unequal (outer 2–3 obtuse, densely pubescent or glabrescent, often gland-dotted, innermost glabrous or glabrescent). Receptacles flat or convex, epaleate. Florets 4–22; corollas usually purplish or pinkish, rarely white, throats funnelform, lobes 5, ovate to deltate; styles: bases enlarged, puberulent, branches ± filiform to clavate (slightly dilated or flattened distally, papillose). Cypselae (dark brown to black or yellowish brown) prismatic, 5-ribbed, usually gland-dotted, sometimes scabrellous on ribs; pappi persistent, of 25–40 (cream to pinkish purple) barbellate bristles in 1 series. x = 10.
Species 5 (5 in the flora): North America.
Detailed distribution maps for taxa of Eutrochium are available but treated as taxa under Eupatorium (E. E. Lamont 1995).
Lamont, E. E. 1995. Taxonomy of Eupatorium section Verticillata (Asteraceae). Mem. New York Bot. Gard. 72: 1–66. Mackenzie, K. K. 1920. Scientific names applicable to our purple-flowered eupatoriums. Rhodora 22: 157–165. Wiegand, K. M. and C. A. Weatherby. 1937. The nomenclature of the verticillate eupatoria. Rhodora 39: 297–306.