Hydrangea \Hy*dran"ge*a\, n. [NL., fr. Gr. "y`dwr water + ? vessel, capsule: cf. F. hydrang['e]e.] (Bot.) A genus of shrubby plants bearing opposite leaves and large heads of showy flowers, white, or of various colors. {H. hortensis}, the common garden species, is a native of China or Japan.