November 13, 1999 Brittanica Staff A large genus of popular herbs of the family Iridaceae much grown for ornament. They have a petaloid six-parted perianth, an inferior ovary and only three stamen (the outer series), being thus distinguished from the Amaryllidaceae, which have six stamens. They are handsome showy-flowered plants, the Greek name Iris ("rainbow") having been applied on account of the hues of the flowers. The genus contains more than 150 species, widely distributed throughout the north temperate zone. The rootstocks of irises may be planted: 1) Shallowly in spring (in colder climates) or 2)Autumn in an open, sunny exposure and well-drained garden soil Propagation is commonly by division of rootstocks just after the flowering period. Irises do not breed true from seed; however, seeds may be planted upon ripening and may germinate the following spring. Although irises thrive under a variety of conditions, mulching is desirable in cold climates. See N.L. Cave, Iris, rev. ed. (1959); Wilma L. Vallette, Iris culture and Hybridizing for Everyone (1961).