[header] How to divide dwarf iris [title] Choose the correct time to divide the rhizomes of the dwarf iris. [step] Divide irises during the summer dormancy period into early fall, at least 6 weeks after the last blooms have faded. This gives the newly formed rhizomes time to become established. 
[substeps] Irises should be divided every 3 to 4 years or when the middle of the clumps look bald. Irises may indicate they need divided when the amount of blooms decrease from year to year.