From The Collaborative International Dictionary of English v.0.48 [gcide]:
Dahlia \Dah"lia\ (d[aum]l"y[.a] or d[=a]l"y[.a]; 277, 106), n.;
pl. Dahlias. [Named after Andrew Dahl a Swedish botanist.]
(Bot.)
A genus of plants native to Mexico and Central America, of
the order Composit[ae]; also, any plant or flower of the
genus. The numerous varieties of cultivated dahlias bear
conspicuous flowers which differ in color.
[1913 Webster]