Irises are classified into two major groups: rhizome irises and bulbous irises. Within those groups are countless species, varieties, cultivars and hybrids, according to the American Iris Society.
Rhizome irises are thickened stems that grow horizontally, either underground or partially underground. After planting, iris rhizomes produce swordlike leaves that overlap, forming flat fans of green foliage. Three popular irises in this group are Bearded, Beardless and Crested irises.
Bulbous irises grow from bulbs that require a period of dormancy after they have bloomed. The bulbous irises are typically smaller than rhizome irises and usually produce smaller blossoms.
The bearded iris has four distinct parts: Standards, Falls, Stigma flaps, Beard
The beardless variety has : Standards, Falls and Stigma flaps, but usually have crests
The crested Irises or Evansia Iris: Standards, Falls and Stigma flaps and in addition to a ridge on the falls of the blossom, they have ridges like crests instead of beards.
