Sp. Pl. 2: 886. 1753.
Gen. Pl. ed. 5, 377. 1754.
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 yellowbrown, 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.
North America, Mexico, West Indies (Cuba), Central America, South America
Species ca. 32 (18 in the flora).
Helenium polyphyllum Small is apparently a hybrid between H. autumnale and H. flexuosum.
|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|
|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|