Lay down a thick layer of CARDBOARD in your raised garden beds to kill the grass. It is perfectly safe to use and will fully decompose, but not before killing any grass below it. They’ll also provide compost and food for worms.
Building My "Special" Raised Garden Beds.Because I needed some protection from the sun in some of my test beds I installed some “removeable” shade cloth. Because these plants bloom better in full sun I only put it on a bed when I am collecting pollen for hybridizing or fertilizing; to protect me from the sizzling sun, then I remove it.