My bearded irises are no longer blooming well. Why?

Bearded irises should be divided every three to five years. If not divided, plants become overcrowded and flower production decreases. July or August is the best time to dig, divide, and transplant bearded irises. 

If bearded iris is planted too deeply, plants will have poor bloom. Bearded irises grow from thick, underground stems called rhizomes. When planted, the rhizome should be at or just below the soil surface. In many cases, the top of the rhizome can be visible at the soil surface.  Occasionally over time a build-up of soil, mulch, or other organic material will place the large fleshy rhizomes too deep underground.  Dig and reset the rhizomes to the proper depth in mid-summer.

Lack of sunlight could be another possible reason for a lack of flowers. Bearded irises bloom best in full sun. Plants need at least six hours of direct sun per day for best flowering. It is possible for established bearded iris plants to be planted in full sun but then become shaded over time when trees and shrubs around them get larger.  Plants in partial shade may not bloom well and should be transplanted to a sunny site.