Cutting back perennials last week I came across a beautiful clump of bearded iris foliage hidden in the garden. I had forgotten that this plant was here because I have not seen it flower in years!
While the rhizomes of Japanese and Siberian Iris can be planted 3 to 4 inches deep, rhizomes of the bearded iris need to be at the surface to have optimum flower performance. Flowering of these rhizomes is diminished over time due to the added depth of seasonal applications of bark mulch, compost and shredded leaves.
This is a good time of year to lift, divide and clean bearded iris rhizomes. Large rhizome clumps should be split to give the plants more room to grow. Check for any signs of iris borer damage. Rhizomes that have been attacked by the borer will have soft or rotten sections and have a foul odor caused by bacteria in the decaying tissue. Remove and discard affected parts of the rhizome by cutting them back to solid tissue. Replant rhizomes by covering the roots but have a good bit of the rhizome showing at the surface.