Summer/ Fall: The best time to transplant irises is usually in late summer till early fall. During this period, the iris must have bloomed enough.Temperature: Transplant your irises when the temperature is around 40 degrees and 50 degrees Fahrenheit or above.
Iris plants usually get overcrowded so you will need to divide your iris plant. Overcrowding of the iris plant can subject the rhizome to lose its liveliness and stop generating good blooms. Therefore, one of the important ways of caring for your iris plant is to divide and transplant.
Sometimes we might get a little busy and forget to check on the iris plant if it’s overcrowded. You can divide and transplant your iris in spring and still get a bloom. But sometimes you may not get a bloom. So there you have your options.