Mulch/mʌltʃ/ Definition 1 of 2Pro Tip 1/3Gardening Term Mainly used in gardening to describe a protective ground covering. Adding mulch in the spring can enrich the soil. Pro Tip 2/3Variety of Materials Mulch can be made from many different materials, not just leaves. She used straw as mulch for her vegetable garden. Pro Tip 3/3Soil Improvement Mulch is used to improve soil health by adding nutrients as it decomposes. Organic mulch can add vital nutrients back into the soil.