You know, it's a good question. I hadn't really thought about it, but I tend to turn the iris beds into mixed plantings. I like to create a garden as ecologically balanced as I can -- good for the native wildlife and so on. I don't even think about it consciously, I guess, but I do it. It's probably because before I got the iris virus -- which I REALLY have in a bad way now, lol -- before that, I was mostly into native plants. They were what led me to irises through a back door. My husband and I used to backpack all the time in the Sierra Nevadas. One of the wild flowers I liked most in the Sierras was/is Iris hartwegii. (Now you know why I am "IrisHart" -- short for Iris hartwegii.) I knew I couldn't easily grow hartwegiii in a suburban back yard, but I decided regular irises were the next best thing. And, THEN I stumbled upon REAL garden irises, meaning the stunning range of colors and varieties developed by avid hobbiests over the years. I was doomed from then on. You all know what it's like. LOL.
Anyway, because I started with native plants, I tend to work my native plants in with the irises. I start out with an iris-only bed, but then gradually compatible natives get in there, too. I like the combinations, I like bringing the birds and butterflies in, giving the poor bees safe pollen to harvest, cover for California quail, and the natives are compatible with bearded irises. All are drought resistant (necessary here in SoCal), hardy, tend to go dormant in the summer, and so on.
Here are some examples:
This shows Festuca californica forming a meadow around irises -- such as in this case Larry Lauer's "My Generation."
Here are yet more tall beardeds with Festuca californica. There is also Festuca glauca here and there -- and we have Zauschneria in the meadow, but you usually can't see it until it blooms in late summer.
This last photo shows IB "Devil May Care" with native red sage, yarrow, and Coreopsis.