There are several common problems that could be preventing your irises from blooming:
Overcrowding: Irises that are clumped too tightly together may stop blooming and will benefit greatly from being divided. Simply dig your irises up—being careful to leave most roots intact—and separate the plants’ rhizomes from one another with a sharp blade. Each division should consist of a sizable rhizome, several roots, and at least one fan of foliage. The best time to divide and replant irises is mid-summer, as this gives the irises a good chance to reestablish themselves and (hopefully) bloom in subsequent springs. Freshly replanted irises should be given ample water for several weeks after they are planted.
Lack of sunlight: Irises bloom best when they receive at least half a day (6 hours) of full sun. If your irises are receiving too little light, they may not flower.
Over-fertilization: Too much nitrogen can encourage irises to grow foliage instead of flowers. Lawn fertilizers contain large amounts of nitrogen, so avoid exposing irises to these.
Too much or too little water: Irises prefer well-draining soil, so make sure your irises are not getting swamped with water, which can lead to root or rhizome rot. Irises do not need to be planted very deep in the ground and should be allowed to dry out a little before their next watering. Depending on your local climate, irises can be watered once or twice a month in the summer.
Dealing with one or more of the above issues should get your irises back to blooming. Good luck!
There are several common problems that could be preventing your irises from blooming:
Dealing with one or more of the above issues should get your irises back to blooming. Good luck!