Coastal Plain Trumpetweed

Eutrochium dubium is restricted to the coastal plain, and inland along major river systems, of eastern North America. Identification of E. dubium has been difficult for field botanists, as evidenced by misidentified herbarium specimens. The most prominent character distinguishing E. dubium from its relatives (especially E. maculatum) is the 3-nerved leaf venation: the proximalmost pair of lateral veins are more prominent and more prolonged than the others. This character is best observed on abaxial leaf faces.

Plants 40–120(–170) cm. Stems usually purple-spotted, sometimes uniformly purple, solid, glabrous proximally, glandular-puberulent distally. Leaves mostly in 3s–4s; petioles 7–25 mm, glabrous; blades usually ± 3-nerved, rarely pinnately veined, deltate-ovate or ovate to lance-ovate, 5–16 × 2–8 cm, relatively thick and firm (often rugose), bases usually abruptly contracted to petioles, margins coarsely serrate, abaxial faces densely gland-dotted and sparingly hirsute (at least on midribs and main veins), adaxial faces scabrous, glabrescent. Heads usually in ± convex, sometimes flat-topped, corymbiform arrays. Involucres often purplish, 6.5–9 × 2.5–5 mm. Phyllaries glabrous or sparsely hairy. Florets (4–)5–9(–10); corollas usually dark purple, rarely pinkish or white, 4.5–7 mm. Cypselae 3–4.5 mm. 2n = 20.

Eupatorium dubium Willdenow ex Poiret in J. Lamarck et al., Encycl., suppl. 2: 606. 1812; Eupatoriadelphus dubius (Willdenow ex Poiret) R. M. King & H. Robinson; Eupatorium americanum Hill; E. ternifolium Elliott

Eutrochium dubium, also called coastal plain joe pye weed, is a North American flowering plant in the family Asteraceae. It is native to the eastern United States and Canada, primarily the Atlantic coastal plain from Georgia to Nova Scotia.

Eutrochium dubium is a herbaceous perennial plant herb sometimes as much as 170 cm (68 inches or 5 2/3 feet) tall. Stems are sometimes purple, sometimes green with purple spots. The plant produces numerous flower heads in flat-topped arrays, each head has 4-10 dark purple (rarely pink or white) disc florets but no ray florets. The flowers are attractive to birds.

Eutrochium dubium prefers full sun to part shade. It will grow in a variety of soil types, provided the soil does not dry out.