There are grass specific herbicides that can be oversprayed safely on iris beds, but the effective ones are extremely expensive. Alternately, if your iris clumps are small, you can trim back the leaves to 6", then cover them with plastic food containers, coffee cans, etc. to protect them while you spray with RoundUp. You can protect larger clumps by covering them with buckets or garbage cans while you spray. RoundUp is reasonably priced and very effective at killing just about everything, both grassy and broadleaf.

Or you can dig all the irises out, then spray the bed with RoundUp, wait two weeks, and replant.

Laurie

Laurie,
Thanks for the info. I like the idea of cutting down the leaves and putting a cover over the plants. Then use Roundup, unfortunately, my favorite herbicide. August is a good time? The bed is about 20 x 10, so it won't take long. Some of the German iris have been in the family since the 1880's- direct from relatives who migrated here from Germany. We've moved them several times over the years. So, I want to keep them going. I'll also start digging and dividing them more often.