Certified GKH Gardening Expert
Most grass in garden beds can be easily pulled up (though it may be time consuming) and followed with the addition of a 1/2" thick layer of (moist) newspaper topped with 2" mulch. You can also use a non-selective herbicide, such as glyphosate (Roundup), which has the potential to kill any plant on contact. However, with care this can be used as a spot spray in flower beds, avoiding contact with desirable plants. Don't do this on a windy day. If feasible, you might want to cover your candy tuft with trash bags while you spray, and for about half an hour after. It will dry rather quickly, kill the grass, and will not stay in the soil.