Eupatorium rotundifolium
Eupatorium leucolepis
round-leaf boneset, round-leaf thoroughwort, roundleaf eupatorium
justiceweed, white-bract thoroughwort
(from short rhizomes) single, sparsely branched distally, puberulent.
(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);
sessile or subsessile;
blades ± 3-nerved, usually ± deltate to orbiculate, sometimes ovate, 15–50(–70) × 15–40(–60) mm (lengths mostly 1–2 times widths), bases broadly rounded to truncate, margins crenate to serrate, apices acute, faces puberulent to villous, 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 3–4 mm.
5;
corollas 3–3.5 mm.
8–10 in 2–3 series, elliptic to oblanceolate, 2–6 × 0.5–1.5 mm, apices acute, 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.
2–3 mm;
pappi of 30–40 bristles 3.5–4 mm.
2–3 mm;
pappi of 30–40 bristles 4.5–5 mm.
Eupatorium rotundifolium
Eupatorium leucolepis
Varieties 3 (3 in the flora).
Eupatorium rotundifolium is one of the more variable species of the genus; its apparent propensity to hybridize with other species has led it to be described as a compilospecies and has complicated its delimitation. Hybrids with E. perfoliatum and E. sessilifolium are sufficiently distinctive to be treated here as distinctive entities (E. ×cordigerum and E. godfreyanum, respectively), and the varieties ovatum and scabridum have also been proposed to be of hybrid origin. The boundaries between varieties are indistinct and individual specimens may be difficult to place with confidence.
(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 3-nerved from bases, bases subtruncate to broadly cuneate, margins crenate | var. rotundifolium |
1. Leaf blades 3-nerved distal to bases, bases broadly cuneate to cuneate, margins serrate | → 2 |
2. Leaf blades 30–70 × 30–60 mm, broadest nearmiddles | var. ovatum |
2. Leaf blades 20–50 × 15–30 mm, broadest nearbases | var. scabridum |
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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