Flora of North America species comparison

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Eupatorium semiserratum

Eupatorium lancifolium

smallflower eupatorium, smallflower thoroughwort

lanceleaf thoroughwort
Habit Perennials, 40–100+ cm. Perennials, 40–100+ cm.
Stems

(from short rhizomes) single, densely branched distally, puberulent throughout.

(from short rhizomes) single, branched distally, usually glabrous or glabrate, sometimes pilose.
Leaves

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);

sessile or subsessile (petioles to 5 mm);

blades 3-nerved from bases, lanceolate to lance-linear, 30–50 × 5–13 mm, bases narrowly cuneate, margins serrate, apices acute, faces glabrous adaxially, sparsely pilose abaxially, densely gland-dotted.
Florets

5;

corollas 2.5–3 mm.

5;

corollas 2.5–3 mm.
Phyllaries

7–10 in 2–3 series, elliptic, 1–3 × 0.5–1 mm, apices rounded to acute (not mucronate), abaxial faces puberulent, gland-dotted.

7–10 in 2–3 series, elliptic, 1–4.5 × 0.2–0.8 mm, apices rounded, abaxial faces pilose, gland-dotted.
Heads

in corymbiform arrays.

in corymbiform arrays.
Cypselae

1.5–2 mm;

pappi of 30–40 bristles 2.5–3 mm.

2.5–2.8 mm;

pappi of 30–40 bristles 3.5–4 mm.
2n

= 20.

= 20.

Eupatorium semiserratum

Eupatorium lancifolium
Phenology Flowering Aug–Sep. Flowering Aug–Sep.
Habitat Moist to boggy, sandy, peaty soils, margins of pine flatwoods, gum swamps, bayheads, disturbed sites, roadsides Dry, rolling terrain, clay soils, shade to sun, shortleaf pine and oak woods
Elevation 10–100+ m (0–300+ ft) 50–200+ m (200–700+ ft)
Distribution
from FNA
AL; AR; FL; GA; LA; MS; NC; SC; TN
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; LA; TX
[BONAP county map]
Discussion

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.)

Eupatorium lancifolium has been combined with E. semiserratum or listed within it as a subspecies; it differs in its habitat as well as in having leaves that are somewhat smaller, typically a dull blue-green (in contrast to yellow-green in E. semiserratum), and 3-nerved from bases of blades.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 21, p. 473. FNA vol. 21, p. 468.
Parent taxa Asteraceae > tribe Eupatorieae > Eupatorium Asteraceae > tribe Eupatorieae > Eupatorium
Sibling taxa
E. album, E. altissimum, E. anomalum, E. cannabinum, E. capillifolium, E. compositifolium, E. godfreyanum, E. hyssopifolium, E. lancifolium, E. leptophyllum, E. leucolepis, E. linearifolium, E. mikanioides, E. mohrii, E. perfoliatum, E. petaloideum, E. pilosum, E. resinosum, E. rotundifolium, E. serotinum, E. sessilifolium, E. ×cordigerum, E. ×pinnatifidum
E. album, E. altissimum, E. anomalum, E. cannabinum, E. capillifolium, E. compositifolium, E. godfreyanum, E. hyssopifolium, E. leptophyllum, E. leucolepis, E. linearifolium, E. mikanioides, E. mohrii, E. perfoliatum, E. petaloideum, E. pilosum, E. resinosum, E. rotundifolium, E. semiserratum, E. serotinum, E. sessilifolium, E. ×cordigerum, E. ×pinnatifidum
Synonyms E. cuneifolium var. semiserratum E. parviflorum var. lancifolium, E. semiserratum var. lancifolium
Name authority de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 177. (1836) (Torrey & A. Gray) Small: Fl. S.E. U.S., 1167. (1903)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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