What's the plural of iris

Last fall I was tasked by my wife to help thin out the irises. Apparently you have to get rid of about a third each year for them to do well.
In the flower bed the irises were very thick in some places and very thin in others. So instead of trashing the flowers that we were thinning, we just moved them to the thin sections. At the time we didn't realize what we were doing, but when the bloomed the other day we were very pleased. The irises are now intermingled, with different colors spread throughout the whole bed. Check it out.