Do ireses (the flower) have a "life span", an age after which they stop blooming?
Answers:
Actually most irises do not produce after the first year. The iris is a rhizome (similar to a bulb) and divides every year. When people think of irises, they usually think of the tall bearded irises, which are usually 36 inches tall or a bit more. The first year you will usually have one stem on the iris with blooms. After that, even though the 'mother plant' is (or may be) alive, it has multiplied and there are three or so new plants. These will be the ones that bloom the second year. The third year there may be six, seven, eight or maybe more under ideal conditions, in a clump that may be a foot or more across and may need dividing which is done in the late summer or early fall. Plant tall bearded irises about 18 inches apart if you don't want to divided them the second year. (They will probably need divided the third year). Dutch irises by the way are bulbs, not rhizomes.
Most tall bearded irises love the sun, even here in Arizona where I live. Your question asked about the age they stop blooming and I wanted to point out that if they get too crowded they may stop blooming so plant them far enough apart that they won't be crowded and good luck!
Sam Wymer
Other answers:
I don't think they have a certain number of years that they bloom, but you do need to divide them every few years. Irises have large roots (tubers) that can be broken apart like bulbs. If they become too crowded, they will not bloom any longer. Just dig them up and pull them apart or use a shovel to cut the tubers apart, then replant them and they will bloom again next year. Hope this helps.
I don't think they have a certain number of years that they bloom, but you do need to divide them every few years. Irises have large roots (tubers) that can be broken apart like bulbs. If they become too crowded, they will not bloom any longer. Just dig them up and pull them apart or use a shovel to cut the tubers apart, then replant them and they will bloom again next year. Hope this helps.