Answer: Since your tulips are in a raised planter you should be able to place a barrier over the top of the planter to keep digging critters out. I'd plant the bulbs as usual and then cover over the top of the planter with chicken wire or bird netting. Find some with one inch or 1 1/2 inch holes or use bird netting that you can easily cut to accommodate the sprouting foliage. If the wire or bird netting is firmly attached to the edges of the planter you'll effectively keep out cats, rats, mice and other digging critters.
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