Finding the key to success with garden mulches

Mulch is any protective material placed on the soil surface to help prevent moisture loss through evaporation, to moderate soil temperatures, prevent weed establishment, enrich the soil, reduce erosion and to highlight and connect hard landscape structures with the soft texture and aesthetic of plant materials.

Some of the best mulches are organic such as leaf litter, wood chips, graded barks and finer products like sugar cane mulch, pea straw and lucerne hay but there are also inorganic mulches and aggregates that perform admirably in some garden situations.

Succulent gardens can come to life with scoria, decomposed granite or pebbles as a decorative mulch.

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A common criticism of organic mulches with a high percentage of relatively fine material is their propensity to being hydrophobic, meaning they tend to repel water.

Hydrophobic mulches produce complex acids as the organic matter decomposes, a wax-like substance can develop and coat the mulch surface.

Wetting agents, a common addition to potting mixes and landscape soil blends, are now being incorporated into some commercial mulches to improve water penetration.

The key to success with mulches lies in selecting an appropriately graded material applied at the correct thickness.

Ideal mulches allow water and air to enter and exit the soil. They should be attractive, preferably odour free, stay in place and should not compact or become a potential fire hazard.

Although no single mulch material will meet all these requirements, selecting one that best suits the needs of the garden will ensure success.

Always apply mulch to a moist soil, preferably after rain, to lock in the moisture and keep mulch thickness to around 50 millimetres. Mulching container plants is also recommended, but keep it away from the stems.

Groundcover plants can be classed as living mulch and provide all the same benefits.

They are also exceptional for stabilising slopes and preventing soil erosion, suppressing weed growth and an excellent way of attracting beneficial insects into the garden and providing habitat for lizards, frogs, and invertebrates such as beetles.