We have to move irises by the beginning of May to make room for a vegetable garden. Everything I read says they must be transplanted between July and September. Will I lose them all if I do not in May? Is there anything I can do to save even some of them?
The ideal time for dividing, lifting or transplanting is after they are done blooming, usually in the summer.
It isn't always feasible to time things to the ideal moment, and in the case of Iris, they are quite hardy and you can certainly go ahead and move then now.
You may have a few less flowers this year, but they will recover quite quickly.
I myself will be moving an entire planting as soon as the ground thaws, as I'm also making some garden changes.