I have a bed of Improved Golden Sedum that is healthy in every way, but wants to go back to lawn. This is difficult to weed, because the grass has a very dense shallow root system, while the Sedum has soft thin roots. Pulling the grass would take out a large part of the Sedum, and leave holes in the ground. How can I successfully this grass while maintaining the Sedums health? here is a picture of how it looks after weeding. It is normally dense and tall.
Mulch helps a lot in this kind of situation. I'm thinking of ordinary pine/cedar/hemlock bark mulch. Before mulching, cut the grass as low as you can, or pull the tops off if it's too intermingled in the sedum to cut. When the grass grows through the mulch the roots are a lot shallower, and there's less of it. Because the roots are shallower, and because the soil underneath is moister, pulling grass without harming the plants around it becomes a lot easier. But resign yourself to losing some of the sedum when you do weed it. It will grow back!