It is a good idea and its helpful to mulch as it:
- Inhibits weed germination and growth. (Weeds are not only unsightly, but they also steal resources from desirable garden plants!) and
Holds in soil moisture, protecting your plants from drying out quickly not to mention it:
- Moderates soil-temperature fluctuations (This benefit is especially valuable during that turbulent-weather period in spring when you don't want your plants to be stressed.)
- In cold-winter areas, protects plant roots from winter cold and helps prevent frost-heaving, in which plants are literally pushed out of the ground by the natural expansion and contraction of the soil as it cools off and heats up
- In hot-summer areas, helps keep plant roots cooler
