Helianthus (sunflower) is a genus of plants comprising about 52 species in the Asteraceae family, all of which are native to North America. The common name 'sunflower' also applies to the popular annual species Helianthus annuus. This and other species, notably Jerusalem artichoke (H. tuberosus), are cultivated in temperate regions as food crops and ornamental plants. The genus is one of many in the Asteraceae that are known as sunflowers. It is distinguished technically by the fact that the ray flowers, when present, are sterile, and by the presence on the disk flowers of a pappus that is of two awn-like scales that are cauducous (that is, easily detached and falling at maturity). Some species also have additional shorter scales in the pappus, and there is one species that lacks a pappus entirely.