This will cut them up and cause bleeding. If you are reluctant to kill them, you can go out at night with a flashlight and pick them off the plants. I have some persistent woodchucks . I build some fencing that goes two feet below the ground. The area is terraced and the wood chucks still get in the garden.
Poisons are out of the question.
My experience with woodchucks has taught me to out smart them. They have elaborate tunnels, that have drains and other amenities. Terraces are prime targets for these wise animals. I found that the Havaheart traps will work, if you have patience and guile. Bait the traps with crackers and peanut butter.