Thinning Bearded Iris Clumps

Iris need to be thinned or divided before they become overcrowded, generally every 3-4 years. If Iris are allowed to become too crowded the bloom will suffer, some varieties may crowd others out and disease problems may be aggravated. August or September is the time to divide and transplant Bearded Iris. Old clumps may be thinned by removing the old divisions at the centers of the clumps and leaving new growth in the ground. Or, you may dig up the entire clump and remove and replant the large new rhizomes.