Mulch is an organic protective cover placed over the soil. There are many benefits to using mulch in garden beds. Mulch helps retain water in the soil by slowing down the evaporation process. Mulch also controls weeds by blocking out sunlight. Mulch helps control the temperature of the soil by retaining heat in the spring and fall and keeping the soil cool on hot summer days. Mulch also helps repel insects. Below are some common types of mulch and their benefits.