The genus Helianthus Linnaeus

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.

aug_26_07m.gthmb can't be loaded. Plants of the Helianthus genus (the Sunflowers) are annuals or perennials. Their capitula are usually radiate, and borne singly or in arrays. Their phyllaries are persistent. They usually have ray florets with yellow corollas and a large number of disk florets. Their fruit is a cypsela, usually purplish black. There are 52 species in the genus, and the 52 are found in North America (the original habitat of the genus is the American continent). The species (including one hybrid) that one can find in Québec are: The number of chromosomes of the Helianthus genus (n) is 17.

The identification of Helianthus species has long been problematic. Taxonomic difficulties are based on a combination of factors, notably developmental and ecologic plasticity, the frequency of interspecific hybridization, and the presence of polyploidy; the taxonomic rank of certain taxa is still (2007) problematic.

The genus belongs to the Asteraceae family.


In classical Greek ανθοσ (anthos) means flower, and ηλιοσ (êlios) is the sun. The genus scientific name refers to the flower heads that are somewhat sunlike when blooming or because the flower heads somewhat follow the sun by day, always turning towards its direct rays (heliotropism) hence the French common name Tournesol, although Helianthus flower heads do not follow the sun across the sky any more than other plants. And the genus common English name is just a translation of the scientific name or vice-versa.