About every three years you may notice that the center of each iris patch has stopped blooming. That means the rhizome is dead. It's time to dig them up, divide them, and replant. This is usually done in August. You can use a pitchfork to dig them up. You can break up the clumps by hand. Some might be dried out, full of holes, or even mushy. Get rid of all of those. Cut the green tops into fans. Replant the healthy ones with one third of the rhizome above soil level. Spread them out six or eight inches apart. If you have extras share them with friends and neighbors. You can always sprinkle a little bulb food in the hole before planting to help things along. Give them a good watering to let them settle in for next year.