Mulches for Home Grounds: Preventing Nitrogen Deficiency
When should mulch be applied?
Mulches used to enhance appearance and control weeds may be applied at any time. If the mulch will be used to protect fall transplants by keeping soil temperatures above freezing longer into the fall (permitting better root growth), apply soon after transplanting. Reapply or refresh organic mulches after they have begun to break down.
If the mulch is meant to reduce frost heave and delay spring growth, apply after the ground has frozen. This type of mulch often is used to protect small bulbs such as scilla and crocus and to prevent early emergence.