Eupatorium semiserratum
Eupatorium leucolepis
smallflower eupatorium, smallflower thoroughwort
justiceweed, white-bract thoroughwort
(from short rhizomes) single, densely branched distally, puberulent throughout.
(from short caudices or stout rhizomes) single, sparsely branched distally, puberulent throughout (more densely distally and among heads).
usually opposite (distal sometimes alternate, lateral buds dormant or producing 1 pair of leaves); simple, sessile or subsessile;
blades ± 3-nerved distal to bases, elliptic to lance-elliptic, (30–)50–70 × 5–25 mm (lengths mostly 2–5 times widths), bases narrowly cuneate, margins usually serrate, apices acute, faces puberulent or villous, densely gland-dotted.
usually opposite (distal sometimes alternate, ascending to vertical);
sessile;
blades pinnately nerved, lance-oblong to linear-oblong, 20–60 × 4–10(–15) mm, bases rounded to cuneate (not connate-perfoliate), margins entire or serrate, apices acute, faces villous (abaxial), scabrous (adaxial), gland-dotted.
5;
corollas 2.5–3 mm.
5;
corollas 3–3.5 mm.
7–10 in 2–3 series, elliptic, 1–3 × 0.5–1 mm, apices rounded to acute (not mucronate), abaxial faces puberulent, gland-dotted.
8–10 in 2–3 series, narrowly elliptic, 2.5–8 × 0.8–1.2 mm, acuminate to attenuate, mucronate, abaxial faces puberulent, gland-dotted.
in corymbiform arrays.
in corymbiform arrays.
1.5–2 mm;
pappi of 30–40 bristles 2.5–3 mm.
2–3 mm;
pappi of 30–40 bristles 4.5–5 mm.
= 20.
Eupatorium semiserratum
Eupatorium leucolepis
Eupatorium semiserratum has been included within E. glaucescens (E. cuneifolium); it is distinguished by its consistently smaller heads and stems that branch only within the capitulescences. It differs from the similar and sometimes sympatric E. lancifolium by its smaller heads, leaves 3-nerved distal to bases (rather than at bases), as well as preference for wetter habitats. It has been proposed that E. rotundifolium var. scabridum (E. pubescens) represents hybrids between E. semiserratum and E. rotundifolium; it also apparently hybridizes with E. hyssopifolium.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
Eupatorium leucolepis is distinct morphologically by its acuminate to attenuate phyllaries, linear and usually plicate leaves, and phyllotaxy that is almost always strictly opposite to the arrays, with well-separated nodes. Eupatorium leucolepis has recently been shown to include two distinct species, an unnamed diploid that is endemic to Carolina Bay habitats and a series of relatively widespread and mostly polyploid, apomictic populations that include the type. It was recognized after preparation of this treatment that E. novae-angliae (E. leucolepis var. novae-angliae) was derived from hybridization between the unnamed diploid and E. perfoliatum, and is here recognized as a distinct species; it is not directly related genetically to E. leucolepis and thus is not appropriately classified as a variety of it.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf blades strongly folded along midribs, curved, 4–10 mm wide | var. leucolepis |
1. Leaf blades weakly folded along midribs, not curved, 10–15 mm wide | var. novaeangliae |
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