Eutrochium

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.

Distribution

North America.

Discussion

Species 5 (5 in the flora).

Detailed distribution maps for taxa of Eutrochium are available but treated as taxa under Eupatorium (E. E. Lamont 1995).

Selected References

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.

Lower Taxa

Eutrochium dubium, Eutrochium fistulosum, Eutrochium maculatum, Eutrochium purpureum, Eutrochium steelei

Key

1	Leaves usually ± 3-nerved and bases of blades abruptly contracted to petioles; florets (4–)5–9(–10) (near coast from South Carolina to New Hampshire and Nova Scotia)	Eutrochium dubium
1	Leaves either pinnately veined or bases of blades gradually narrowed to petioles or both; florets 4–10 or 8–22	> 2
2	Heads in ± flat-topped arrays; florets 8–22	Eutrochium maculatum
2	Heads in convex to rounded arrays; florets 4–10	> 3
3	Stems usually glandular-pubescent throughout, sometimes densely puberulent and sparingly glandular; abaxial leaf faces ± glandular-pubescent and sparsely hirsute; s Appalachian Mountains of sw Virginia, e Kentucky, e Tennessee, and w NorthCarolina	Eutrochium steelei
3	Stems glabrous proximal to heads; abaxial leaf faces sparingly and minutely gland-dotted; relatively widespread in e North America	> 4
4	Stems purple at nodes, usually solid, rarely ± hollow near bases	Eutrochium purpureum
4	Stems purplish throughout (and glaucous), hollow	Eutrochium fistulosum