I spent a lot of time clipping off bloomstalks with bee pods forming. I always miss a few and get a few seedlings blooming near an established clump each year.
It seems like the ones the bees make are really hardy and if I did not dig them out when I first spot them they would manage to take over the space of the desired iris. I look for little new irises that are not connected to the clump when I am weeding too. I can just pull them out with the weeds. I have some areas set aside for seedlings and no room for any more.
If one or two bloom and they are really lovely.... then they are keepers.