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.
I just wanna upcycle some wooden pallets and call it a bed, yknow? Love this,cheap,easy n recycling . It will eliminate need for box spring n bed frame. I just got 10 wooden pallets does couple of nefty projects n this is on my list for my guest room :-)