Mulch can be applied anytime throughout the year. However, because of the insulating properties of mulch, some seasons are more desirable than others. In the cold winter months, apply it only 1 inch thick to insulate the ground to prevent soil warming. Since spring is the planting season, remember to push aside mulch from newly planted seeds, seedlings, and bulbs. In a vegetable garden, mulching should not be done until the tomatoes blossom. In the fall when mulching around transplants, a 5 inch coverage is needed to delay frost penetration, allowing more time for root growth.