Eutrochium dubium
Eutrochium
coastal plain joe-pye weed, joepye thoroughwort
eupatoire, joe-pye weed
usually purple-spotted, sometimes uniformly purple, solid, glabrous proximally, glandular-puberulent distally.
(sometimes ± purple, sometimes glaucous, internodes usually shorter than leaves) erect, unbranched.
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.
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.
often purplish, 6.5–9 × 2.5–5 mm.
cylindric, 2.5–7 mm diam.
flat or convex, epaleate.
(4–)5–9(–10);
corollas usually dark purple, rarely pinkish or white, 4.5–7 mm.
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).
glabrous or sparsely hairy.
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).
usually in ± convex, sometimes flat-topped, corymbiform arrays.
discoid, in (flat-topped or convex to rounded) compound, corymbiform arrays.
3–4.5 mm.
(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.
= 10.
= 20.
Eutrochium dubium
Eutrochium
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.)
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).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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) | E. 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 | E. 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 | E. 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 | E. purpureum |
4. Stems purplish throughout (and glaucous), hollow | E. fistulosum |
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