juniper trimmings. your dog will not like the way these poke the soft pads on their paws when they try to enter the garden.
perhaps, my favorite mulch deterrent idea for keeping dogs away from garden plants might help. simply create moats of pine cones around the garden or even just around specific plants. like the trimmings from thorny shrubs, your dog will not like the way the pines cones feel on its paws, and the pine cone moats will look like you just added a decorative, natural accent to the garden.
the battle between dogs and plant protection is much simpler when the problem is your own dog. you can watch 