Mulches are the first line of defense from weeds and weather. They insulate plant roots from winter freezes and protect soil moisture from summer heat. If thick enough, mulches prevent weed seeds from germinating and cut down on crabgrass, thistles and other weeds that invade your yard. While you can place mulch in your yard year-round, time your application to coincide with your yard's needs for the best results.
While renewing mulch in springtime is a standard gardening chore, timing the application depends on your yard's needs. Mulching in early spring before crocus, daffodils and forsythia emerge smothers potential weeds before they gain a toehold in your flowerbed. Mulching at this time also keeps winter-chilled soil cool and delays growth of heat-loving annuals. If your yard has problems with spring weeds, apply much before the soil warms. Likewise, if you have mature perennial plantings with few weed problems, mulch in late spring.
Mulching your yard in fall has two major benefits. First, fall applications in colder zones protect newly installed plants -- which lack an established root system -- from heaving out of their sites during seasonal freeze-thaw cycles. Second, fall is a perfect time for savvy gardeners to harvest fallen leaves or raid their compost piles. Shredded leaves are an excellent, if short-lived, mulch and quickly return nutrients to the soil. The mulches decay through winter and give spring plants an extra boost.
While you may be tempted to mulch your established plants before cold temperatures frost the leaves, this may harm your plants. Chilly roots signal to the plant that it's time to slow growth and store nutrients. If you apply an insulating layer of mulch before temperatures drop, the plant continues growing until a hard frost stops it in its tracks. Instead, mulch after the ground freezes. This layer of mulch keeps frozen ground protected from unseasonal thaws and plants safe in their dormant state.
Add a layer of mulch whenever your install new plantings, keeping the mulch 1 to 2 inches out from tree or shrub trunks. Also, don't overlook your vegetable garden. Spread 2 to 3 inches of mulch in early spring to extend cool-season crops such as peas or broccoli. For tomatoes, peppers and other heat-loving crops, mulch in late spring when the soil warms to 70 degrees.