Iris flowers comprise 6 parts. There are 3 inner parts or the standards. These are generally upright. There are 3 outer parts or the falls. These are reflexed and are often bearded at the base.
Standards are large and showy in most species, but reduced in the Japanese irises.
Three style branches arch over the anthers or pollen-bearing portion of the stamens, and the stigma or the structure that receives the pollen, is on the underside of the branches near the end. This morphological arrangement essentially forms a tunnel through which pollinating insects have to travel. Iris specialization and hybridization has lagged behind that of some other genera, but now there is an almost unbelievable array of cultivars available. Species and cultivars may be selected for diverse situations, ranging from woodland to rock gardens, for sites along streams and around ponds, and for the herbaceous or mixed perennials beds and borders. Each series has 5 to 25 species.