Mulching herbs can help prevent heaving of the plants and help ensure winter survival. Winter mulching should not be done until the weather turns cold or it could cause the plant to be less hardy. For perennial herbs, a 2 - 3 inch layer is adequate. For tender perennial herbs, a 3 - 6 inch layer should be added. These tender herbs should be cut back to 3 inches, but only after the plant has gone dormant. An additional measure of protection should be added by covering the plant with soil and then adding a four-inch layer of mulch on top of the soil. This is done after the first frosts, but before a hard freeze. Annual herbs should be pulled to prevent spread of disease.