Fl. N. Amer. 2: 333. 1842.
Perennials, 20–150 cm. Stems erect, usually branched. Leaves basal and cauline; opposite (proximal) and alternate; usually petiolate (at least proximal); blades (usually 3- or 5-nerved from at or near bases) elliptic, lanceolate, lance-linear, linear, oblanceolate, ovate, ovate-lanceolate, or spatulate, bases mostly cuneate, margins entire, faces glabrous or hairy. Heads radiate, borne singly or (2–15+) in corymbiform arrays. Involucres campanulate to hemispheric or broader, 10–50 mm diam. Phyllaries persistent, 22–32+ in ± 3 series (mostly deltate-ovate or ovate to lanceolate, linear, or oblong, subequal or unequal, outer sometimes foliaceous). Receptacles ± convex, paleate (paleae falling with cypselae, conduplicate, scarious or chartaceous). Ray florets 8–21, neuter; corollas ± yellow. Disc florets 30–200+, bisexual, fertile; corollas yellow or purple to brown, tubes shorter than or equaling throats, lobes 5, deltate (abaxially hairy). Cypselae (brownish) ± compressed, obovate to obcordate (margins usually ± winged, usually ± ciliate, faces glabrous or strigose); pappi 0, or persistent, of 2 ± subulate scales plus 0–4+ shorter, lacerate scales (sometimes all ± connate). x = 15.
w North America, n Mexico.
Species 9 (6 in the flora).
|1||Heads 5–15+; phyllaries mostly deltate-ovate to oblong (unequal to subequal); ray laminae 8–14+ mm (usually little surpassing discs); disc corollas purple to brown||Helianthella microcephala|
|1||Heads 1(–3+); phyllaries mostly lanceolate, lance-linear, lance-oblong, or ovate (subequal, outer sometimes foliaceous); ray laminae (11–)15–30(–45+) mm; disc corollas yellow||> 2|
|2||Heads ± nodding; paleae scarious, relatively soft||> 3|
|2||Heads erect; paleae chartaceous, relatively firm||> 4|
|3||Plants 20–50 cm; leaf blades oblanceolate or spatulate (broadest distal to middles, not leathery), faces rough-pubescent; involucres 15–20 mm diam.; ray florets 8–14 (corollas pale yellow)||Helianthella parryi|
|3||Plants usually 50–150 cm; leaf blades elliptic to ovate-lanceolate (broadest near middles, leathery), faces sparsely hirsute or glabrous; involucres 40–50 diam.; ray florets (13–)21 (corollas bright yellow)||Helianthella quinquenervis|
|4||Cauline leaves: largest at mid stems; faces of cypselae strigose||Helianthella uniflora|
|4||Cauline leaves: largest proximal to mid stems; faces of cypselae usually glabrous||> 5|
|5||Involucres 15–20(–25) mm diam. (sometimes 2–3 outer phyllaries foliaceous); cypselae strongly compressed||Helianthella californica|
|5||Involucres 25–40 mm diam. (usually 3–4+ outer phyllaries foliaceous, 3–10+ cm); cypselae weakly compressed (plump in middles, thin at edges)||Helianthella castanea|