Greek helios — sun, opsis — appearance, as the showy capitula resemble the sun.
Annual or perennial herbs, often fleshy. Stems erect, loosely branched. Leaves along stems, mostly opposite, margins toothed, petiolate. Capitula radiate or diskoid, terminal, solitary or in loose cymes, with stalks. Involucral bracts in 2 or 3 rows, overlapping, unequal. Receptacle with scales, conical, often hollow. Ray florets female, usually ligulate, yellow, orange or purple. Disk florets bisexual, tubular, yellow, brownish or purple. Achenes 3- or 4-angled. Pappus of up to 3 small scales, a toothed crown or absent.
Large showy capitula; pappus of scales, a crown or absent.
15 species from N, C and S America, especially Mexico.
Source: (2002). Dahlia. In: . Horticultural Flora of South-eastern Australia. Volume 4. Flowering plants. Dicotyledons. Part 3. The identification of garden and cultivated plants. University of New South Wales Press.