231. Helianthus Linnaeus, Sp. Pl. 2: 904. 1753.
向日葵属 xiang ri kui shu
Annuals or perennials. Stems erect or ascending to decumbent or procumbent, usually branched distally. Leaves basal and/or cauline, opposite, opposite (proximal) and alternate, or alternate, petiolate or sessile; blade mostly deltate, linear-lanceolate, lanceolate, ovate-lanceolate, linear, or ovate, both surfaces glabrous or hairy, often gland-dotted, base cordate to narrowly cuneate, margin usually entire or serrate, rarely lobed. Synflorescence of solitary capitula or of corymbs, panicles, or spikes. Capitula usually radiate or sometimes discoid; involucres usually hemispheric, sometimes campanulate or cylindric; phyllaries persistent, in 2 or 3+ series, subequal to unequal; receptacle flat to slightly convex or conical; paleae conduplicate, usually rectangular-oblong, usually 3-toothed, sometimes entire, apices sometimes reddish or purplish. Ray florets usually 5-30, rarely 0, neuter; corollas usually yellow. Disk florets numerous, bisexual, fertile; corollas yellow or reddish, tubes shorter than campanulate throats, lobes 5, triangular. Achenes usually purplish black, sometimes mottled, ± obpyramidal, ± compressed; pappus absent or readily falling, of 2(or 3) usually lanceolate, aristate, or erose scales plus 0-8 usually shorter scales, 0.2-2 mm. x = 17.
About 52 species: North America; three species (all introduced) in China.
See Heiser et al., Mem. Torrey Bot. Club 22(3): 1-218. 1969.
Helianthus angustifolius Linnaeus, H. argophyllus Torrey & A. Gray, H. atrorubens Linnaeus, H. decapetalus Linnaeus, H. ×laetiflorus Persoon, H. maximiliani Schrader, and H. mollis Lamarck are cultivated in China.