Marilyn - I have usually only gotten those leaves after unusual weather, such as our on and off very warm/very cold winter. I can see the obstruction argument. It is like too many leaves are trying to push out from a small area of the rhizome. I also notice that I get the crinkles more on new iris. Those that have been here a couple of years or more tend to not get it so much. But then, the rhizomes have also changed their shape by then too. Longer and narrower. Which I am sure is a heat dissipation adaptation.
