Eutrochium dubium
coastal plain joe-pye weed, joepye thoroughwort
usually purple-spotted, sometimes uniformly purple, solid, glabrous proximally, glandular-puberulent distally.
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.
often purplish, 6.5–9 × 2.5–5 mm.
(4–)5–9(–10);
corollas usually dark purple, rarely pinkish or white, 4.5–7 mm.
glabrous or sparsely hairy.
usually in ± convex, sometimes flat-topped, corymbiform arrays.
3–4.5 mm.
= 20.
Eutrochium dubium
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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