Interesting idea. I never thought of that. My iris does not stop the grass except where it it is . I think IRIS is everywhere because it is hard to kill iris and it slowly self replicates and one has to de vide it every three years and then many peole give it away to friends and neighbors. So iris spreads by the sharing of the overage.

Nothing blocks Bermuda !!! ( for me)!

I have to weed around my iris just like everything else :-)