Eupatorium linearifolium
Eupatorium pilosum
waxy thoroughwort
ragged thoroughwort, rough boneset
(from short caudices) single or multiple, branched at or near bases, pubescent throughout.
(from short rhizomes) single, sparsely branched distally, densely puberulent to pilose throughout.
usually opposite (distal sometimes alternate);
sessile or subsessile;
blades 3-nerved distal to bases, oblong to lance-oblong, 20–45 × 5–10 mm, bases cuneate, margins entire or serrate (teeth mostly proximal), apices acute, faces finely puberulent, gland-dotted.
usually opposite (distal sometimes alternate); simple, sessile or subsessile;
blades ± 3-nerved (distal to bases), elliptic, lanceolate, or lance-ovate, 30–90 × 20–45 mm (lengths mostly 2–2.5 times widths), bases rounded to rounded-cuneate, margins unevenly serrate, apices acute to attenuate, faces puberulent, gland-dotted.
5;
corollas 3–3.5 mm.
5;
corollas 3.5–4 mm.
8–10 in 1–2 series, lanceolate (tapering toward apices), 2–5 × 0.5–1 mm, apices rounded to acute, abaxial faces puberulent, gland-dotted.
7–10 in 2–3 series, oblong to lance-oblong, 2–7 × 1–1.5 mm, apices (sometimes whitish) acuminate to acute, mucronate, abaxial faces puberulent, gland-dotted.
in corymbiform arrays.
in corymbiform arrays.
2.5–3 mm;
pappi of 30–40 bristles 3–5 mm.
3–4 mm;
pappi of 30–50 bristles 4–5 mm.
= 20, 30, 40.
= 20, 30, 40.
Eupatorium linearifolium
Eupatorium pilosum
Plants treated here as Eupatorium linearifolium were long treated under the name E. cuneifolium; the latter name was superfluous when published (K. N. Gandhi and R. D. Thomas 1991). Because there appears to be a continuous range of variation between diploids that were referred to by V. I. Sullivan (1972) as E. cuneifolium and the series of putative hybrids (with E. hyssopifolium suggested as the other parent) that she called E. linearifolium, these are combined here. The tendency for the plants to branch at or near the bases is distinctive within Eupatorium.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Eupatorium pilosum has been most commonly treated as a variety of E. rotundifolium; it is distinct morphologically by its leaves, which are narrower and 3-nerved distal to bases, rather than 3-nerved from bases. Distal leaves of E. pilosum tend to differ from the proximal by being alternate with entire margins.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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