I have a problem with couch grass in my perennial beds. I've tried a lot of things (including digging up entire beds and painstakingly removing the grass roots), but this method seems to work pretty well to CONTROL (not eradicate) couch grass. You sort of "kill it with kindness." I found that if I put down a good layer of loose mulch...wood chips are ideal...over the course of a few months, especially as the lower levels of the mulch begin to decay/compost, the couch grass begins to migrate "upward" into the mulch layer and out of the soil, seeking the better nutrients and moisture in the decaying mulch. The trick is to keep the mulch moist, either with rainfall or regular watering (which is good practice for any perennial bed). Once the couch grass migrates up into the mulch layer, it's a lot easier to pull it out and I can often pull some very long lateral roots out of the ground. It's certainly not a fast solution to eradicating couch grass, but it does work well to control it and over time...years I would think...if you are dedicated about pulling the grass as it emerges, you can eventually get rid of couch grass.

If you also dig a trench around the bed the couch grass will not be able to move from one area to another. That way you can fight the enemy in a small, controlled area.

Or instead of the trench, you could insert a barrier - something like aluminum roof flashing, or vinyl siding created a 'no runner zone', again confining the couch grass to one area while you wage war.

That's a great idea! I'll definitely try that when I can.

Excellent advice. A barrier can also be weed-trimmed against, severing any runners that try to jump over it.

When mowing, aim the chute away from beds if the grass has any seeds on it.

For existing patches, you could pull the mulch back, lay cardboard on it, cover thickly with mulch, to weigh it down and block all of the light. That should be the end of the grass, as long as it's undisturbed until the grass is truly dead, and covers the patch completely. If seams are necessary, overlap at least 6" so grass can't find the crack to exploit. If left alone, the cardboard will decompose and does not need to be removed. Even works wiregrass, and bahiagrass. Our yard has those and others, not hard to keep out of beds once eliminated.

with @purpleinopp about the cardboard - excellent and easy solution.

I will definitely try all these suggestions. Where I have most of my problem is that the couch grass gets twined through existing plants, so it's hard to lay down cardboard. But if i use mulch, the grass sort of "rises to the top" and I can eventually get it out. THANKS EVERYONE!

Wonderful idea, Annie. When the weeds are easy to pull out, it's not at all such a problem.

Here, it's wire grass I struggle with. Barriers make it laugh. But making the soil loose and moist, heh. Kill it with kindness. I like it!