The upper parts, known as standards, curve up into a dome. Three curved stylebranches cover the stamens in the center. The colors of irises range through all shades and appear in many combinations. Some iris rhizomes are bulblike, but most are elongated. Iris rhizomes contain a poison, and eating them can cause severe stomach upset.
Irises grow throughout the temperate regions.
These perennial plants bloom from April through July. They may be planted in spring before blooming, or in autumn. The plants with rhizomes give the best flowers if replanted about every four years. The most common garden irises are the tall bearded varieties. There are thousands of different kinds.