Edging of beds and walkways to give that clean sharp look. Mulching needs to be done once per year. This can be done at anytime of the year, be it spring, summer, fall or winter. Most gardeners in New England and NH choose to mulch in the spring because that is when they are cleaning up the garden for the year ahead and before a lot of weeds begin to emerge. We like to keep a depth of 2 to 3 inches the mulch.