Trimming back the foliage will accomplish two goals: it tidies them up aesthetically and it protects against iris borers. A moth lays eggs on the foliage in summer. The eggs over winter on the foliage then hatch in spring. The grubs then travel down the foliage and destroy the rhizome. (Its called a borer because it bores into the rhizome). So yes, you definitely do want to trim back iris foliage in fall. I cut mine to a fan shape about the size of the palm of my hand. I'm in the DC area & trimmed mine a couple of weeks ago.

This is how they should look when you are done..These are my 2 years old seedlings

wow this is such a helpful post ... both the text and the photos.... I was just wondering the same thing.

I haven't cut mine back but I guess i'll do it this week asap ...

thanks so much.

This post was edited by toronto.and.brisbane on Mon, Sep 8, 14 at 23:41

1) What are the best types of irises for Tucson? I moved from the East coast and am thrilled that I can still enjoy them.

2) Looks like I missed the planting season, can I buy them in bloom in the spring?

I never cut mine back in the fall. I am in 7. I just do a good clean up in the spring.. The only time I cut back is when I am transplanting them.

I used to never cut back my iris, from Texas to Virginia to Maryland to New Jersey and back to Virginia. Never had a problem. A couple of years ago I about lost everything to iris borers. It seems the very best thing to do is cut them back, remove all dead foliage, and make sure to haul all of it away. I used to compost it, but I don't even do that now. I may even apply nematodes once it warms up in the spring to make sure they are all gone. For so many years, the variety of colors, size of blooms, and overall beauty of my iris was spectacular, but for the last couple of years I've had almost nothing as it is all rebuilding. If cutting back helps the recovery and can prevent future infestations, it is well worth it.

So far we don't have a lot of borer here, and so I've never cut mine back until spring. If I lived in the east I would do it for sure. Many people do it here anyway, and their iris are pretty just like mine.