Bearded iris plants are touted as being easy to grow plants for the landscape, but they do have certain needs that must be met in order produce their best flowers. The two most frequently reported causes for diminished blooms in bearded iris are lack of sunlight and overcrowding of the plants.  Irises typically require full sun, at least 6 hours a day.  They will produce foliage in the shade, but they won’t bloom well.  If shade is encroaching on your iris bed, you may need to relocate the plants to a sunnier spot.

Irises also need space to bloom. After a few years in the ground, the iris rhizomes will start to get crowded, which can lead to fewer blooms over time.   Examine the soil around the bases of the plants.  If you see a tangle of rhizomes with some being pushed out of the ground, it is probably time to thin the plants out. In late summer or early fall, dig and divide the clumps, discarding the older,non-productive areas of rhizome.

Bearded iris usually need to be divided every three to five years. Here are some links with information about dividing your iris plants:

https://kansashealthyyards.org/all-videos/video/dividing-iris

https://hgic.clemson.edu/give-your-bearded-irises-some-space-divide-them/

If your irises are not crowded and are getting full sun, there are some other possible reasons why they might be blooming sparsely.  Overfertilization with nitrogen is one possibility.  When excessively applied to the soil, nitrogen will stimulate leafy, vegetative growth in plants at the expense of fruit and flowers.  This lush, green growth can be tender and susceptible to insect pests and diseases.   In this scenario, you might need to change your fertilizing practices.  Iris are reported to require little or no supplemental fertilization, but if additional nutrients are needed, many extension websites recommend using a slow-release fertilizer with nutrient ratios of 5-10-10 or similar.

https://www.canr.msu.edu/news/fertilizing_established_perennial_gardens_feed_em_and_weep

Then there’s the weather.  Iris plants, like spring flowering bulbs, have a bloom period, followed by a dormant or semi-dormant period.   During this resting phase, the rhizomes and roots carry out biological processes to prepare the plant for the next growing season.  Any adverse weather conditions that occur during the year