Set the cage in the bottom of the hole, and let the top of the cage lie open (figure A). Add soil along the bottom of the cage if necessary to make planting depth adjustments within the cage. Position the bulbs in the cage, and cover with soil, tamping down gently as you work. Close the cage lid, and cover the entire box with soil. If you need additional protection or if the cages aren't your style, consider using a mixture of crushed oyster shells (figure B). Mixed with soil, the shells form a rough-edged, irritating barrier that rodents are reluctant to cross. Simply combine two to three tablespoons of shells into the planting hole. Add another tablespoon or two with the soil used to fill the hole. "In addition, oyster shells are an excellent source of calcium and are loaded with other nutrients from vegetable protein meal and peanut meal," says James, "plus they have some potassium and a teeny pinch of magnesium." So the shells not only protect your bulbs, they also feed them.
Why not get rid of the pests in the first place? James says catching rodents isn't as easy as it seems. Preventative methods like the bulb cage and oyster shells allow you to spend your time doing what you like instead of chasing after pesky pests.