A genus of plants native to Mexico and Central America, of the order Compositæ; also, any plant or flower of the genus. The numerous varieties of cultivated dahlias bear conspicuous flowers which differ in color.
The Aztecs cultivated the dahlia, which grows wild in Central America and Mexico, and Spanish explorers brought the flower to Europe. It was named for Anders Dahl, a Swedish botanist. Wild dahlias are flat, with a yellow center and eight single scarlet rays. Modern varieties may be globe-shaped and double, or with many petals. Their color may be white, yellow, orange, red, or purple. The plants grow from 18 inches to 20 feet (46 centimeters to 6 meters) high. They bloom in late summer or autumn. Dahlias may be grown from seed or cuttings, by grafting (to perpetuate rare varieties), or by division of the tuberous roots. Amateur gardeners commonly use the last method. After frost kills the tops, the tubers should be divided and then stored in a cellar. Dahlias form a genus of the family Compositae. Thousands of varieties of dahlias have been developed from hybrids of Dahlia pinnata and D. coccinea.