Here is a weed which is sadly infesting my iris bed. It runs underground and puts up new leaves. Eventually, this plant has a tiny yellow flower cluster. I have tried getting rid of it by putting on rubber gloves, THEN cotton gloves over top, then dipping fingers in Roundup and rubbing the liquid (on the cotton gloves) on the plants I want to be rid of. Doesn't seem to work really well. Anybody can help me? First, what is it? Second, how to get rid of when you have a lot of plants you want to keep nearby? Thanks everybody!