This article is about the flower; there is also a P. G. Wodehouse character named Dahlia Travers.

30 species, 20,000 cultivars

Dahlia is a genus of bushy, summer- and autumn-flowering, tuberous perennials that are originally from Mexico, where they are the national flower.

In 1872 a box of Dahlia roots were sent from Mexico to the Netherlands. Only one plant survived the trip, but produced spectacular red flowers with pointed petals. Nurserymen bred from this plant, which was named Dahlia juarezii with parents of Dahlias discovered earlier and these are the progenitors of all modern Dahlia hybrids. Ever since, plant breeders have been actively breeding Dahlias to produce hundreds of cultivars, usually chosen for their stunning and brightly coloured flowers.

Modern popular varieties include:

Dahlia 'Moonfire'

Dahlia 'Bishop of Llandaff'

The dahlia is named after Swedish 18th-century botanist Anders Dahl.