There are several groups of beardless irises recognized by gardeners. In fact, some gardeners are devoted to just one of these groups. Some of the Siberians will cross with the Californicas resulting in a hybrid group called Cal-Sibes. Unfortunatly, they're nearly always infertile. Japanese irises are bred from a species in the series Laevigatae .
Bearded irises are the most popular irises.
These interbreed with the true bearded iris to produce what are called Arilbred irises.