Helianthus

Helianthus is a genus of flowering plants in the family Asteraceae, native to North America. The genus comprises about 70 species of annual and perennial herbs, including the well-known sunflower (Helianthus annuus) and the Jerusalem artichoke (Helianthus tuberosus). Helianthus species are grown for seeds and oil, as ornamentals, and, in the case of H. tuberosus, for edible tubers.

Plants are typically tall with sturdy, hairy stems and large, rough leaves. Each inflorescence is a single flower head (capitulum) with yellow ray florets surrounding a central disk of small disk florets that mature into a head of seeds. Some species show heliotropic movement in which the flower head tracks the sun, especially in young plants; cultivated sunflowers generally face east as they mature.

They favor full sun and well-drained soil. Annual species such as H. annuus are grown for edible seeds and oil; H. tuberosus produces edible tubers and is grown as a perennial. Ornamental cultivars are bred for flower size, color, and longevity. They attract pollinators and are used in cut flower arrangements.

The genus is native to North America and includes numerous species occupying prairies, meadows, and disturbed areas. Notable cultivated species are H. annuus and H. tuberosus; many other species are grown ornamentally or studied for traits such as drought tolerance and disease resistance.

Sunflowers are susceptible to pests such as sunflower beetles, wireworms, and seed weevils, and diseases including rust and powdery mildew. Birds frequently harvest seeds. Management relies on integrated pest management, resistant varieties, and proper spacing and sanitation.