Mulch: what to use, how thick, and when
A good layer of mulch keeps soil cool and moist, feeds the soil life and keeps weeds down. Which mulch suits veggies, natives and fruit trees, and how to lay it.
2 min read 路 Patchmates
Mulch is anything you spread over the soil surface. In a dry climate it is one of the most useful things you can do for a garden: it slows evaporation, keeps roots cooler in summer and warmer in winter, smothers weeds and, as it breaks down, feeds the soil.
Which mulch where
| Where | Good choices | Why |
|---|---|---|
| Veggie beds | Pea straw, lucerne, sugar cane | Breaks down in a season and adds organic matter |
| Fruit trees | Coarse wood chips, composted bark | Lasts longer, good for deep-rooted plants |
| Natives | Coarse wood chips, leaf litter, gravel | Natives often prefer low-nutrient mulch |
| Strawberries | Straw | Keeps fruit off the soil and clean |
How thick
- Veggie beds: 5 to 7 cm of straw-type mulch.
- Trees and shrubs: 7 to 10 cm of wood chips.
Too thin and weeds push through; too thick on fine materials and water struggles to get in.
How to lay it
- Weed first, and water the bed well.
- Spread the mulch evenly.
- Pull it back a hand's width from stems and trunks. Mulch piled against stems holds moisture there and can cause rot.
- Water again so the mulch settles.
When
Late spring, before the heat arrives, is the most important time. Top up through summer as it breaks down. In winter you can thin it a little in veggie beds so the sun can warm the soil.
Seedlings and seeds
Mulch around seedlings once they're a few centimetres tall. For seeds sown straight into the ground, leave a clear row until they come up, then tuck mulch in around them.
Does wood mulch rob nitrogen?
Fresh wood chips can tie up a little nitrogen right at the surface where they touch the soil. On trees and shrubs this rarely matters. In veggie beds, use a straw-type mulch or compost instead and keep fresh wood chips for paths.