Along with edging, mulch helps create a defined and well maintained look to your landscape. No more than 3" of mulch should exist throughout your plantings. If there is existing mulch you may only need to top dress with 1-2" every spring.
Occasionally, mulch will begin to build up around your shrubs, trees, and foundations. It is important to remove all this old mulch prior to installing new so that you don't exceed that 3" maximum. Allowing the mulch to build up creates an environment conducive to insects and disease, it also ties up the nitrogen in the soil preventing your plants from being able to use this essential nutrient.
Why is mulch so important? By applying mulch, you will help minimize weed growth, help with moisture retention in the soil, and regulate the ground temperature.