Eupatorium album
Eupatorium
white thoroughwort
thoroughwort
(from short caudices or stout rhizomes) single, sparsely branched distally, pubescent throughout.
erect, usually not branched proximal to arrays of heads (from caudices or rhizomes).
usually opposite (distal sometimes alternate);
sessile;
blades ± 3-nerved or pinnately nerved, elliptic to oblanceolate, 30–120 × 10–40 mm (lengths mostly 3–4 times widths), bases narrowly cuneate (sometimes oblique), margins subentire, serrate, or serrulate, apices rounded to acute, faces setulose (denser on midribs and veinlets) to glabrate, usually gland-dotted.
mostly cauline; usually opposite (rarely whorled, distal sometimes alternate); petiolate or sessile;
blades usually 3-nerved from or distal to bases, or pinnately nerved, mostly deltate or ovate to lanceolate or linear (and intermediate shapes, sometimes elliptic, oblong, rhombic, or suborbiculate, sometimes pinnatifid, 1–2-pinnately, ternately, or palmately lobed), ultimate margins entire or toothed, faces glabrous or puberulent, pubescent, scabrous, or setulose, usually gland-dotted.
obconic to ellipsoid, 1–3(–5+) mm diam.
flat or convex, epaleate.
(4–)5;
corollas 4–4.5 mm.
(3–)5(–15+);
corollas usually white, rarely pinkish, throats funnelform to campanulate, lobes 5, triangular;
styles: bases sometimes enlarged, usually puberulent (glabrous in E. capillifolium), branches mostly filiform.
9–15 in 2–4 series, linear, 1.5–9 × 0.6–1 mm, apices acuminate to attenuate, sometimes mucronate, abaxial faces pubescent throughout, gland-dotted.
persistent, 7–15+ in 2–3(–4+) series, (usually green) 2–3-nerved, or not notably nerved, or pinnately nerved, elliptic, lanceolate, oblong, or obovate, usually unequal, sometimes ± equal (margins scarious, hyaline, apices rounded to acute or acuminate sometimes mucronate, faces usually puberulent or villous, usually gland-dotted, rarely glabrous).
in corymbiform arrays.
discoid, in corymbiform or diffuse to dense, paniculiform arrays.
2.5–3.5 mm;
pappi of 40–50 bristles 3.5–4.5 mm.
(brownish to black) prismatic, 5-ribbed, usually glabrous, usually gland-dotted;
pappi persistent, of 20–50 (whitish) barbellulate bristles in 1 series.
= 10.
Eupatorium album
Eupatorium
Varieties 3 (3 in the flora).
Eupatorium album is represented by widespread diploid populations and by polyploid, apomictic populations, segregated as varieties, that may have arisen by hybridization with other species. Molecular data suggest that var. vaseyi arose via hybridization between var. album and E. sessilifolium. They also suggest that E. album var. subvenosum arose from hybridization between E. album var. album and E. serotinum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species 41+ (24 species, including 2 hybrids, in the flora).
Eupatorium is treated here in a restricted circumscription, following R. M. King and H. Robinson (1987) in excluding genera that traditionally have been included in a broad Eupatorium (e.g., Ageratina, Chromolaena, Critonia, Conoclinium, Fleischmannia, Koanophyllon, Tamaulipa); Eutrochium (Eupatorium sect. Verticillatum) is also excluded here.
Species identification within Eupatorium is sometimes complicated; polyploidy and apomixis have contributed to the complications. Some species include both sexual diploid and apomictic polyploid plants or populations. V. I. Sullivan (1972) made important contributions to understanding Eupatorium in North America by showing that some fairly distinct, sexual diploid species may include apomictic polyploid plants or populations that do not differ greatly from the diploids. Other apomictic polyploids appear to be intermediate morphologically between pairs of diploid or diploid/polyploid species and were proposed by Sullivan to have originated from interspecific hybridization. Distinction and level of recognition of hybrid apomictic taxa have a large arbitrary component, in part because some apomicts appear to be ephemeral and others may be relatively stable and in part because differences in the relative genomic contributions of the progenitors through dosage effects or backcrossing may affect whether an apomict is morphologically distinctive or part of a continuous series of variation.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf blades: margins coarsely serrate, apices obtuse to rounded, faces pubescent | var. album |
1. Leaf blades: margins subentire, serrulate, or serrate, apices acute, faces pubescent to glabrate | → 2 |
2. Leaf blades 3-nerved from bases, 40–70 × 10–20 mm, margins subentire to serrulate | var. subvenosum |
2. Leaf blades 3-nerved distal to bases, 50–110 × 20–40 mm, margins evenly serrate | var. vaseyi |
1. Leaves (at least the principal) pinnatifid, or pinnately or ternately lobed, or palmately 3(–5)-lobed | → 2 |
1. Leaves simple (not lobed, margins crenate, entire, laciniate, serrate, or serrulate) | → 6 |
2. Leaves (at least larger proximal) palmately 3(–5)-lobed (lobes relatively broad, margins serrate; corollas usually pinkish) | E. cannabinum |
2. Leaves pinnatifid or pinnately or ternately lobed (lobes relatively narrow; corollas usually white) | → 3 |
3. Leaves (mostly ternately or 1–2-pinnately lobed): blades or lobes linear; heads in subcorymbiform to subpaniculiform arrays; florets 7–9 | E. ×pinnatifidum |
3. Leaves (usually pinnately or ternately lobed or pinnatifid): blades or lobes linear; heads in paniculiform arrays; florets usually 5 | → 4 |
4. Stems glabrous (gland-dotted, branches supporting heads recurved and secund) | E. leptophyllum |
4. Stems puberulent (branches supporting heads not recurved or secund) | → 5 |
5. Leaf blades or lobes 0.2–0.5(–1) mm wide (margins strongly revolute); phyllaries usually glabrate or glabrous, usually not gland-dotted | E. capillifolium |
5. Leaf blades or lobes 0.5–2.5(–4) mm wide; phyllaries usually puberulent(mostly on midveins), usually gland-dotted | E. compositifolium |
6. Leaves petiolate (petioles 10–30 mm) | → 7 |
6. Leaves sessile or subsessile (petioles 0 or 1–10 mm) | → 8 |
7. Leaf blades deltate to rhombic (held vertically; stems green); florets 5 | E. mikanioides |
7. Leaf blades lanceolate (held horizontally; stems sometimes reddish to purplish);florets 9–15 | E. serotinum |
8. Florets 7–11 (leaf bases connate-perfoliate) | E. perfoliatum |
8. Florets (4–)5–8 or 9–14 (leaf bases not connate-perfoliate) | → 9 |
9. Florets usually 9–14 | E. resinosum |
9. Florets (4–)5–8 | → 10 |
10. Phyllary apices (usually white) acuminate to attenuate | → 11 |
10. Phyllary apices (usually with narrow white margins, sometimes pigmented) acute, obtuse, or rounded | → 15 |
11. Leaf bases (especially larger leaves) clasping to narrowly connate-perfoliate (leaf faces rugose); florets 5–8 | E. ×cordigerum |
11. Leaf bases attenuate, cuneate, or rounded (leaf faces relatively smooth); florets (4–)5 | → 12 |
12. Leaves 4–10(–15) mm wide | E. leucolepis |
12. Leaves mostly 10–45 mm wide | → 13 |
13. Leaves little, if at all, gland-dotted; phyllaries glabrous, not gland-dotted (the larger 8–10 mm) | E. petaloideum |
13. Leaves usually gland-dotted; phyllaries puberulent to villous (at least toward bases and on midveins), gland-dotted (the larger 5–10 mm) | → 14 |
14. Leaf blades elliptic to oblanceolate (lengths mostly 3–4 times widths), bases narrowly cuneate (sometimesoblique); phyllaries linear (larger 6–9 mm) | E. album |
14. Leaf blades elliptic, lanceolate, or lance-ovate (lengths mostly 1–2 times widths), bases rounded to rounded-cuneate; phyllaries oblong to lance-oblong (larger 5–7mm) | E. pilosum |
15. Stems glabrous or glabrate proximally (and leaves pinnately nerved, 70–150 mm); leaves: bases truncate to somewhat rounded, facesglabrate (scattered, fine hairs) | E. sessilifolium |
15. Stems usually pilose, puberulent, or pubescent proximally or throughout (if glabrous, leaves 3-nerved from bases, 30–50 × 5–13 mm, bases narrowly cuneate); leaves (3-nerved from or distal to bases or pinnately nerved): bases usually narrowly to broadly cuneate, rounded, subcordate, or truncate, sometimes clasping to perfoliate, faces glabrous, puberulent, scabrous, or villous. | → 16 |
16. Leaf blades deltate, elliptic, lanceolate, lance-ovate, ovate, or suborbiculate (usually broadest proximal to middles), bases usually broadly cuneate, rounded, subcordate, or truncate, sometimes clasping to perfoliate | → 17 |
16. Leaf blades elliptic, lance-elliptic, lanceolate, lance-oblong, linear, oblanceolate, or oblong (usually broadest near or distal to middles), bases cuneate | → 20 |
17. Leaf bases (especially larger leaves) clasping to narrowly connate-perfoliate (faces conspicuously rugose); florets 5–8 | E. ×cordigerum |
17. Leaf bases broadly cuneate, rounded, subcordate, or truncate (faces smooth to somewhat rugose); florets (4–)5 | → 18 |
18. Leaves pinnately nerved, blades usually 50–100 mm | E. godfreyanum |
18. Leaves 3-nerved, blades 15–50(–90) mm | → 19 |
19. Leaf blades elliptic, lanceolate, or lance-ovate (lengths mostly 2–2.5 times widths, usually with purple borders, sometimes visible only in live plants; distal leaves sometimes alternate) | E. pilosum |
19. Leaf blades usually deltate to suborbiculate, sometimes ovate (lengths mostly1–2 times widths; distal leaves sometimes alternate) | E. rotundifolium |
20. Leaves strongly to obscurely 3-nerved from bases | → 21 |
20. Leaves 3-nerved distal to bases, or pinnately nerved, or relatively narrow and obscurely 3-nerved from bases | → 23 |
21. Stems usually glabrous or glabrate (at least proximally), sometimes pilose; leaves 30–50 mm, faces glabrous abaxially | E. lancifolium |
21. Stems pubescent or pilose proximally or throughout; leaves 20–60(–120, the larger usually 50+) mm, faces puberulent, scabrous, or villous abaxially | → 22 |
22. Leaves: margins entire proximally, serrate distally (teeth sharp, antrorse; mid-ribs and 2 major lateral veins prominent) | E. altissimum |
22. Leaves: margins usually laciniate-serrate (teeth ± divergent; 2 major lateral veins usually obscure) | E. hyssopifolium |
23. Leaves usually in whorls (3s or 4s), sometimes opposite, blades lance-linear to linear (lengths 6–40 times widths) | E. hyssopifolium |
23. Leaves usually opposite (sometimes whorled in E. semiserratum), blades elliptic, lance-elliptic, lance-oblong, oblanceolate, or oblong (lengths 2.5–7 times widths) | → 24 |
24. Leaves (spreading): blades adaxially finely puberulent or villous (stems from short caudices or rhizomes) | → 25 |
24. Leaves (ascending, recurved, or spreading): blades adaxially glabrous or glabrate (stems from tuberous-thickened rhizomes, not usually apparent until flowering is well under way) | → 26 |
25. Stems densely branched distally; leaf blades (30–)50–70 mm, margins usually serrate; phyllaries elliptic (larger 2.5–3 mm); corollas 2.5–3 mm | E. semiserratum |
25. Stems usually branched at or near bases; leaf blades mostly 20–35(–45) mm, margins weakly serrate to subentire; phyllaries lanceolate (larger usually 4–5 mm); corollas 3–3.5 mm | E. linearifolium |
26. Leaves (usually spreading or ascending): blades 15–50 × (5–)10–20 mm | E. anomalum |
26. Leaves (usually recurved): blades 20–80 × 5–10(–20) mm | E. mohrii |
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