I do cut back the fans in the fall, but I have mild winters so they tend to grow and grow. For me, cutting them back in the fall keeps the leaves from falling over from bad weather/snow/ice. I don't keep tree leaves or pine needles over the rhizomes over winter any more because the soil stays way too wet. And I leave potted iris out with the rest of the iris in the beds. Ice storms are the biggest threat here to iris.
