Annuals or perennials, 10–160 cm. Stems 1(–10), erect, simple or branched distally (usually ± winged by decurrent leaf bases), glabrous or sparsely to densely hairy. Leaves usually mostly cauline; mostly alternate (proximal sometimes opposite); petiolate or sessile; blades mostly elliptic, lanceolate, linear, oblanceolate, oblong, ovate, or spatulate, often pinnately lobed or pinnatifid, ultimate margins entire or toothed, faces glabrous or sparsely to densely hairy, gland-dotted. Heads radiate or discoid, borne singly or (2–300+) in paniculiform to corymbiform arrays. Involucres ± globose, hemispheric, obconic, or ovoid, 4–34 mm diam. Phyllaries persistent, 9–34(–40+) in (1–)2[–3] series (distinct or proximally connate, usually reflexed in fruit, glabrous or sparsely to densely hairy, gland-dotted). Receptacles conic, ± globose, hemispheric, or ovoid, pitted (glabrous), epaleate (rarely bearing setiform enations). Ray florets 0 or 7–34, pistillate and fertile or neuter; corollas yellow, yellow with purple streaks, reddish brown to red proximally and yellow distally, or reddish brown to red or purple throughout. Disc florets 75–1000+, bisexual, fertile; corollas yellow, purple, or yellow to yellow-green proximally and yellow-brown, brown or reddish brown to purple distally, tubes shorter than throats, lobes 4 or 5, ± deltate (style-branch apices penicillate or truncate). Cypselae mostly obpyramidal, 4–5-angled, glabrous or sparsely to densely hairy; pappi persistent, of 5–12 entire or ± lacerate, sometimes aristate scales. x = 17.

Distribution

North America, Mexico, West Indies (Cuba), Central America, South America.

Discussion

Species ca. 32 (18 in the flora).

Helenium polyphyllum Small is apparently a hybrid between H. autumnale and H. flexuosum.

Selected References

None.

Lower Taxa

Helenium amarum, Helenium arizonicum, Helenium autumnale, Helenium bigelovii, Helenium bolanderi, Helenium brevifolium, Helenium campestre, Helenium drummondii, Helenium elegans, Helenium flexuosum, Helenium linifolium, Helenium microcephalum, Helenium pinnatifidum, Helenium puberulum, Helenium quadridentatum, Helenium thurberi, Helenium vernale, Helenium virginicum

Key

1	Stems not winged	Helenium amarum
1	Stems ± winged (by decurrent leaf bases)	> 2
2	Ray florets usually 8–34, neuter (if rays 0, perennials from e or se United States)	> 3
2	Ray florets usually 7–30, pistillate, fertile (if rays 0, plants either perennials from w United States or annuals)	> 8
3	Heads 1(–3); disc corollas mostly yellow, sometimes yellow-brown distally	> 4
3	Heads 1–80+; disc corollas usually purple, sometimes red-brown or yellow-brown distally or throughout	> 6
4	Pappus scales deeply lacerate; e Texas, sw Louisiana	Helenium drummondii
4	Pappus scales entire or slightly lacerate (never deeply lacerate); se Louisiana, s Mississippi, s Alabama, s Georgia, se South Carolina, s North Carolina, Florida	> 5
5	Leaves of basal rosettes usually pinnatifid; peduncles hairy; cypselae hairy	Helenium pinnatifidum
5	Leaves of basal rosettes usually entire; peduncles usually glabrous, sometimes sparsely hairy; cypselae glabrous	Helenium vernale
6	Heads (1–)5–50(–80); pappi of aristate scales	Helenium flexuosum
6	Heads 1–20; pappi of non-aristate scales	> 7
7	Stems densely hairy proximally; leaves moderately to densely hairy; pappi 0.3–0.5 mm; nc Arkansas	Helenium campestre
7	Stems glabrous proximally; leaves glabrous or sparsely hairy; pappi 1–1.7 mm; se United States	Helenium brevifolium
8	Perennials	> 9
8	Annuals	> 13
9	Stems unbranched or sparingly branched distally	> 10
9	Stems strongly branched distally	> 11
10	Peduncles usually densely hairy; pappi (2.5–)3–4.5 mm	Helenium bolanderi
10	Peduncles sparsely to moderately hairy; pappi 1.3–2.2(–2.7) mm	Helenium bigelovii
11	Rays usually 13–15, sometimes 0, corollas 3.8–10 mm; disc corollas yello to reddish brown or purple distally, lobes 4(–5)	Helenium puberulum
11	Rays 8–21, corollas 10–23 mm; disc corollas yellow to yellow-brown distally, lobes 5	> 12
12	Leaves: basal blades oblanceolate, obovate, or spatulate (withered by flowering), mid blades usually dentate, distal blades entire or dentate; United States and s Canada	Helenium autumnale
12	Leaves: basal blades oblanceolate (usually present at flowering), mid blades usually entire, sometimes dentate; swampy meadows, Missouri, Virginia	Helenium virginicum
13	Pappi of aristate scales	> 14
13	Pappi of non-aristate scales	> 16
14	Disc corolla lobes 4(–5); California	Helenium puberulum
14	Disc corolla lobes 5; Arizona, Texas	> 15
15	Stems weakly winged (leaf bases scarcely decurrent from node to node); cypselae 2–2.9 mm; n Arizona	Helenium arizonicum
15	Stems narrowly winged (leaf bases decurrent from node to node); cypselae 1–1.2 mm; s Texas	Helenium linifolium
16	Involucres globoid and distal leaves entire	Helenium elegans
16	Involucres usually ovoid to obconic (if globoid, distal leaves serrate to undulate-serrate)	> 17
17	Distal leaves serrate to undulate-serrate; disc corolla lobes (4–)5	Helenium microcephalum
17	Distal leaves entire; disc corolla lobes 4	> 18
18	Rays 10–15	Helenium quadridentatum
18	Rays 0	Helenium thurberi