Helianthus L.
Annual or perennial herbs. Lvs opposite below, often alternate above, simple, entire or serrate, pinnately veined. Capitula pedunculate, solitary or in loose corymbs. Involucral bracts in 2-several rows, imbricate, foliaceous. Receptacle flat or convex; scales present. Outer florets sterile, ligulate, yellow. Inner florets ⚥, tubular. Achenes all similar, compressed, not winged but usually with 2 distinct and 2 indistinct angles; pappus 0 or of 2 or more readily caducous scales, rarely small persistent scales also present.
Key
Rhizomatous or tuberous perennial; capitula in loose corymbs of 1-7; involucral bracts 2-4-(5) mm wide
2
Inner involucral bracts ovate-triangular; lower and mid cauline lvs long-cuneate at base; tubers weakly developed or 0
Inner involucral bracts narrow-lanceolate; lower and mid cauline lvs obtuse at base; tubers well developed
67 spp., N., C., and S. America. Naturalised spp. 2 and 1 cultivated hybrid.
![Fig. 24. Involucral bracts of Helianthus. A H. tuberosus; B H. × laetiflorus. © All rights reserved. [Image: 4X4G]](https://data.landcareresearch.co.nz/Image/4X4G/SysPortalPreview)
Fig. 24. Involucral bracts of Helianthus. A H. tuberosus; B H. × laetiflorus. © All rights reserved. [Image: 4X4G]
