|Rhizomatous irises have rhizomes as rootstocks, close to or on the surface, or just below ground-level, which produce linear to sword-shaped leaves, nearly always in basal fans, and simple or branched flower stems. The flowers have 3 upright petals, called standards, and 3 large, pendent or spreading petals, called falls.
Pacific Coast group irises lack the "beard" of colored hairs at the base of each fall that other iris groups have. Irises in this group bloom in mid and late spring; leaves are usually evergreen. Best in mild areas with winter rain and dry summers. They transplant and grow poorly in much of North America. The Dutch cultivar, 'Imperator' blooms in indigo blue.