Is Mulching Leaves in the Spring Good or Bad for Lawns?

Leaf Mulch Benefits

• Your lawn's soil uses the decomposing leaf mulch as a microorganism stimulant, especially during the spring when the ground is warm and friable. For example, earthworms search nutrient-rich lawn areas for sustenance -- they consume the incorporated mulch as they add critical and soluble elements to the environment through their castings, or feces. Without a rich soil habitat, earthworms and microorganisms move away from your lawn. As a result, the turf's thatch, or decomposing layer, thickens and becomes a barrier to moisture and oxygen.

Leaf Preparation

• Your leaves need to be shredded with a lawnmower to work well as a spring mulch. According to the Scotts Company, leaves the size of a dime work well as lawn mulch. While rapidly moving into the turf's soil, small leaf sizes also encourage widespread decomposition through microorganism activity. Choose a morning when your lawn leaves have some dew on them. Run your lawnmower across the lawn several times to cut all the leaves uniformly. Because most grass species grow rapidly in the spring, you also maintain a healthy turf height while mulching your leaves -- your lawn may need at least one mowing session each week in the spring.

Application

• Because your grass is actively growing and photosynthesizing, do not cover the lawn thickly with leaf mulch. In fact, you should be able to see at least one-half inch of turf consistently above the mulch layer. Use a rake to evenly distribute the leaf mulch into the turf if you have an uneven application after mowing. The exposed grass still photosynthesizes optimally while benefiting from the decomposing leaf matter at the soil level. The moment the mulch enters the soil, microbes gear up for a feast that ultimately increases your turf's vigor and resilience to stress, especially with summer heat on the horizon.

Improper Lawn Mulch Use

• If you do not shred the leaves, or you spread the mulch too thickly on the lawn, you create a barrier to sunlight, moisture and air movement. As a result, the soil below has a limited supply of nutrients that eventually will cause grass dieback. As spring warms the ground, pathogens and pest larvae may proliferate under the thick mulch layer -- your grass becomes a laboratory for disease and pest reproduction. By applying the leaf mulch in a thin layer during the spring, your lawn grows in a healthy environment as it readies itself for summer heat.