Mulch is a many-splendoured thing

Cape Town - After heavy rain, how can gardeners help in a grand environmental quest to protect the topsoil in their gardens? This winter, make a resolution to cover up all the bare soil in your garden with mulch. Bare soil is a barren, gaping wound in your garden that is prone to erosion.

Start by laying a thick blanket of mulch across your garden beds. Top gardeners spend at least 50 percent of their annual garden budget on compost and mulch, as it is this organic matter that keeps the plants in your garden protected and healthy.

Before laying grass as mulch across pathways, ensure that it's dried out first, or it will emit an odour. The actual herbs and vegetable plants in this circular vegetable garden are mulched with dry autumn leaves. Credit: INDEPENDENT NEWSPAPERS

“The quality of food we eat, water we drink, air we breathe and the well-being of all plant and animal life is determined by the quality of our topsoil,” says environmentalist and landscaper Gina Shoemaker. “The earth’s crucial thin layer of soil must be protected, maintained, built and nourished. A thick layer of mulch across the soil enables, conserves and enhances our precious layer of topsoil.”

In healthy woodland, mulch consists of dead leaves, twigs, fallen branches and other plant debris which falls to the forest floor. “Bacteria, fungi and other living organisms use these raw organic materials for food, a process we know as decay. In the natural scheme of things, decay is nature’s way of returning to the earth the raw materials borrowed by previous generations of plants.”

For gardeners, home-made mulch comes in the guise of autumn leaves, which should be packed into a thick layer in garden beds, or superior, commercially-produced mulch, which is available in a wide range of guises from pine bark nuggets to carbon-rich black-composted mulch. “Our winter mulch is a carefully aggregated product that consists of medium to small-sized pine bark compost,” says Earth2Earth’s Donvae Hooker.

“We use pine bark as it has a long residual effect in the soil that enhances and enriches the existing soil structure. The slightly acidic base also stimulates and enhances microbial activity. This process is initiated by earthworms, who reformulate the organic material into a stabilised, long, residual nutrient base within the soil,” she says. “If you are a passionate gardener, choose a mulch that is a certified organic which carries the Bio-Org certification.”

As organic mulch slowly decays over the summer, it not only conserves moisture, but also feeds plants, earthworms, microbes and other beneficial soil life at the surface. Recent scientific experiments carried out in the dry south-west states of the US proves that mulch is very good for your garden.

Mulched soils are much cooler than non-mulched soils and have less fluctuation in soil temperature. “Optimum soil temperatures and less moisture evaporation from the soil surface enable plants to grow evenly. Plant roots find a more favourable environment near the soil surface where air content and nutrient levels are conducive to good plant growth,” adds Shoemaker.

How much mulch do you need?

Large bark chips should be 10cm to 15cm thick, pine needles 5cm to 7.5cm, bagged commercial mulch 5cm to 10cm, leaves 5cm to 10cm, or peanut shells 5cm to 7.5cm.

How many bags will you need?

For a 10cm deep layer of mulch, one 30dm bag will cover 0.3m2 (25 bags will cover 7.5m2). For a 5cm deep layer of mulch, one 30dm bag will cover 0.6m2 (25 bags will cover 15m2).

How to mulch