dahlia däl´yə, dăl´– [key] [for Anders Dahl, 1751–89, Swedish botanist and pupil of Linnaeus ], any plant of the genus Dahlia of the family Asteraceae ( aster family), tuberous-rooted perennials native to Mexico and Guatemala and widely cultivated in gardens. Most of the several thousand horticultural varieties have been developed from the single species ( D. pinnata ) of garden dahlia introduced into cultivation in England c.1800, but other species and hybrids, e.g., the cactus dahlia ( D. juarezii ) are also grown. Dahlias are stout and rather woody plants, some species reaching the stature of small trees, with late-blooming flowers in a wide range of colors and sizes. The tubers of the garden dahlia were one source of fructose, used by diabetics. Dahlias are classified in the division Magnoliophyta , class Magnoliopsida, order Asterales, family Asteraceae.

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