Fall garden cleanup is an essential part of maintaining healthy perennials and shrubs. Trimming back perennials by about two thirds to provide protection for the plant’s crown, and removing spent and diseased foliage will help insure good blooms next summer. 

For the iris bed, a cleanup and trim is a good time to assess the plants and get them ready for winter. Start by pulling out the browned spent foliage. Next trim back the green foliage fans with a diagonal cut angled away from the tubers. This helps to direct water away from the tuber to prevent rot. Remove any diseased or soggy tubers, and pull any grass or weeds that have worked their way into the bed. Avoid the temptation to mulch or otherwise cover the tubers. That could trap moisture and cause rot. They’ll do just fine as they are. 

That should do it.