Mulch is a layer of material that covers the surface of your soil. It can be a living mulch such as groundcovers, an organic mulch such as bark chips, or an inorganic mulch such as gravel or pebbles. It is often neglected in gardens, but plays a vital role in the health of your soil, helping to protect it from erosion, reduce weeds, increase water retention, and to feed nutrients back into the soil (living & organic mulches). Think of our forests; the layers of groundcovers, leaves, sticks and twigs that cover the soil, and you can begin to appreciate the benefits of replicating these aspects in your home. Even our naturally occurring grasslands and savanna (bushveld) regions have very little bare soil (provided they haven't been overgrazed), and instead are covered by low growing grasses and forbs (living mulch).
Here are three types of mulch, their pros and cons, and when to use them:
A living mulch, sometimes known as 'green' mulch or cover crop in agriculture, consists of groundcovers that cover the bare soil of your garden. These are usually low-growing species, either tufted or creeping, that work together to cover the soil and protect it, helping to reduce erosion, increase water retention, limit the growth of weeds, and increase biodiversity. In shaded gardens common species might include Chlorophytum comosum (hen 'n chickens), Plectranthus/coleus species, and Crassula species, whilst in a grassland species might include Eragrostis racemosa or E. nindensis, Sporobolus stapfianus and Microchloa caffra.
Groundcovers, such as Hen 'n chickens, can be used as a living mulch
Organic mulches are materials that are no longer living, but are still organic in nature. These could be dead leaves and twigs that are naturally found in your garden, or products such as bark chips or nut shells, available from your local nursery. Organic mulches can be applied to bare patches of your garden in a layer of about 5-10 centimetres, where they will slowly break down and help to enrich your soil. We use organic mulch in most newly installed gardens, but still prefer to think of it as a temporary solution until the living mulches - the groundcovers - spread and cover the soil.
Chipped wood and shredded leaves can be used an organic mulch until your groundcovers have grown
Inorganic mulches are materials such as pebbles and gravel. They can be used effectively in small spaces such as atriums or in planter boxes, or in larger gardens where you want to create a succulent-themed garden. They come in a range of colours, so you can choose one that matches your garden theme.