Horticulture - Mulching

The horticulturists apply two kinds of mulches to the soil surface in the Gardens.

Organic mulches come from plant material. In use are:

Pine chips – bought from commercial suppliers
Wood chips from recycled branches and trees in the Gardens
Mixture of pine chips and recycled wood chips
Leaf material, typically from Eucalypts, Tea-trees

Mineral mulches come from rocks. In use are:

Chunky granite mix – sand, granite rocks, gravel

Mulches suppress weed growth with the added advantage that organic mulches break down to add organic matter to the soil. They prevent moisture loss and regulate the temperature of the soil. However, mulches can make it hard for water to penetrate, especially if spread too thickly.

Areas in the Gardens with sandy or skeletal soils receive a shallow organic mulch. The Eastern Mallee section, for example, has a mulch of Eucalypt leaves and the needle-like leaves of Tea-trees.

The Ellis Rowan Garden has a mineral mulch of sandy gravel. The mulch allows for good water penetration and simulates the look of a dry river bed.

The pine chips and recycled wood chips are aged before use to avoid the problem of nitrogen drawn down that comes with fresh material. There is no standard amount of mulch used and it varies with the needs of the section.