1. Helianthus annuus Linnaeus, Sp. Pl. 2: 904. 1753.
向日葵 xiang ri kui
Helianthus annuus subsp. jaegeri (Heiser) Heiser; H. annuus subsp. lenticularis (Douglas ex Lindley) Cockerell; H. annuus var. lenticularis (Douglas ex Lindley) Steyermark; H. annuus var. macrocarpus (Candolle) Cockerell; H. annuus subsp. texanus Heiser; H. aridus Rydberg; H. jaegeri Heiser; H. lenticularis Douglas ex Lindley; H. macrocarpus Candolle.
Annuals, 100-300 cm. Stems erect, usually hispid. Leaves mostly cauline, mostly alternate; petiole 2-20 cm; blade ovate-lanceolate to ovate, 10-40 × 5-40 cm, abaxially usually ± hispid, sometimes gland-dotted, base cuneate to subcordate or cordate, margin serrate. Capitula 1-9; peduncles 2-20 cm; involucres hemispheric or broader, 15-40(-200) mm in diam.; phyllaries 20-30(-100), ovate to ovate-lanceolate, 13-25 × (3-)5-8 mm, abaxially usually hirsute to hispid, rarely glabrate or glabrous, usually gland-dotted, margin usually ciliate, apex abruptly narrowed, long acuminate; paleae 9-11 mm, 3-toothed, middle teeth long acuminate, glabrous or hispid. Ray florets (13-)17-30(-100+); lamina 25-50 mm. Disk florets 150-1000; corollas 5-8 mm, throats bulbous at bases, lobes usually reddish, sometimes yellow; anthers brownish to black, appendages yellow or dark. Achenes (3-)4-5(-15) mm, glabrate; pappus of 2 lanceolate scales 2-3.5 mm plus 0-4 obtuse scales 0.5-1 mm. Fl. Jul-Sep, fr. Aug-Oct. 2n = 34.
Open areas. Widely cultivated in China [native to North America].
Helianthus annuus is a major agronomic crop, introduced nearly worldwide.
