Leaf mould, in essence is decomposed leaves. These decomposed leaves break down into a thick, black crumbly substance known as leaf mould. People often confuse leaf mould with leaf mulch. While both these substances come from leaves, leaf mulch is a layer of shredded leaves that is placed on top of the soil, which later breaks down into leaf mould. This is where the confusion often comes from.
While leaf mould doesn’t add many nutrients into your soil, it is a great natural conditioner. Leaf mould aids the soil structure and helps the soil retain moisture. For the best results, you should add a layer of leaf mould to the soil, turn/till it, and then add compost to provide the soil with additional moisture and nutrients.