I divided them several years ago and they do not appear to be overcrowded. I planted them shallow so the tubers are showing to prevent rot. I have used a modest quantity of lime in the soil. They seem to have excellent leaf growth and size. They are mature. Any ideas on why they are relatively unproductive bloomers?
Bearded Iris Blooming Poorly
Certified GKH Gardening Expert
Use a fertilizer higher in phosphorus or even a phosphorus only amendment, like bone meal, to get them to bloom. This article will help you: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/phosphorus-plant-growth.htm
In addition, it can be attributed to poor pollination. Try to entice pollinators (bees, butterflies, etc.) to the area with brightly colored flowers.