Anything that you spray to eliminate the grass will also do great harm to any other plant the spray touches. The best way to eliminate grass from any planting bed is to mechanically remove it. If the wood chip mulch is of the proper thickness the grass should pull out easily, however if that mulch is only an inch thick the grass will be rooted in the soil and be more difficult to remove.

Any attempt to remove this weed by pulling out will be futile at best. It looks like bermudagrass.

There are herbicides that will control grasses without damaging the boxwood: there is that kind of selectivity. I am thinking of Assure or Select. Unfortunately theses are not generally available to homeowners.

You may want to try a few things.
Pull out then apply mulch. I would use a landscape fabric or newspaper (fairly thick, i.e. a dozen sheets), then cover with at least two inches of bark.

You could use RoundUp. pour a little bit in a small container and apply to the grass with a paint brush. You will be pleased.

Good luck

Thanks, I'll see how it goes this weekend when I tackle this.

I'm fighting 3 kinds of invasive grasses with Ortho Weed B Gon. Works great, takes a couple weeks but hasn't damaged any of my plants in the garden areas it's invaded. It comes in a spray bottle and puts out a fine stream easy to direct, has to dry before it rains, won't see anything for awhile, but within two weeks, you can see it is working. And it keeps a lot of it out the following year as well, but not all.

Fertilome makes a similar product. Ortho people tell me it will soon be shipped again; evidently there was a problem with labelling.

I've got a half bottle left I'm hoarding for the worst of it and trying to pull as much of the rest I can get but if you don't get all the roots, it comes right back.

Pre-emergent for the lawn in the spring is another tactic I'm going to try for what's still there that weed 'n feed or 24D won't kill. Also Preen for the garden areas, but that only prevents seeds from germinating, won't do a thing once it's sprouted.

I have never seen on any label of Ortho Weed B Gone that I have looked at that it will control any grass. This product is a broad leaf "weed" poison for use on lawns because it will not kill grasses. A "weed n feed" is also a product to control broad leaf "weeds" and is used on grasses to feed them, not kill them.
If done properly mechanically removing that grass will be much more effective than any expensive spray you can buy. I know people that have sprayed unwanted grasses 4 times during one growing season while I mechanically remove that growing in my planting beds once, maybe twice during the same period and I get the roots the would let more grasses grow later.

Oops, mea culpa, have been looking at too many products.

It's Ortho GRASS B Gon.

Wow, that weed stuff would be bad, thanks for catching it.

the stuff in my beds I've been pulling or chopping with the pointy thing this year which works better than my hoe sometimes. But I can only do that because it isn't mulched, didn't get around to getting bags and bags of that and out of leaves. Stuff comes through mulch, too, but not as bad, used newspaper for the border last year but didn't get it down this year. I can't use too much spray because it's expensive and adds up.

I've also laid cardboard where I can. I put black plastic behind the garage but didn't cover it all, and it's a mess again with weeds, not much grass there. They say black plastic isn't good for the soil.

Yes, I know weed 'n feed and 24D are for broad leaf. I'm stuck with nasty large patches in the lawn that spill over into the garden areas so I want it gone and simply cannot pull it all and get the roots in the lawn, have tried. It's just too hard on my back and so much else to do. Plus it is smothering out all the good grass. This is what you get when you let it go too long.