Mulching fruit trees: what, when and how
How to mulch fruit trees: the best mulches, how deep and how wide to spread them, keeping mulch off the trunk, and when to top it up before summer.
A good layer of mulch is one of the cheapest, most useful things you can give a fruit tree. It keeps the soil cooler and moister through summer, smothers weeds, and feeds the soil as it breaks down. Here is how to get it right.
What mulch does
- Slows evaporation, so water you give lasts longer.
- Keeps the root zone several degrees cooler on hot days.
- Stops weeds competing for water and nutrients.
- Feeds worms and soil life as it breaks down, building better soil over time.
- Stops rain and irrigation compacting and crusting bare soil.
Choosing a mulch
- Pea straw and lucerne break down within a season and add nutrients. Great for feeding the soil, but need topping up often.
- Sugar cane mulch is light and easy to spread, and breaks down at a medium pace.
- Wood chips and shredded prunings last a year or two and suit trees well. Coarse chips let water through better than fine ones.
- Composted mulch feeds the soil and holds moisture, but can wash away on slopes.
Avoid very fine mulch that mats into a crust water can't get through, and avoid plastic weed mat under fruit trees, which starves the soil of air and organic matter.
How to spread it
- Water the soil well first, or mulch after good rain. Mulch keeps moisture in, but it also keeps light rain out of dry soil.
- Pull out weeds and grass under the tree.
- If you like, spread a layer of compost or manure first, then mulch over the top.
- Spread mulch 7 to 10 cm deep (thinner for fine mulches) in a wide circle out to the edge of the canopy or beyond, where the feeding roots are.
- Keep it a hand's width clear of the trunk. Mulch against the bark keeps it wet and invites collar rot and pests.
When to mulch
Top up mulch in late spring, before the heat arrives, and check it again in midsummer. A light top-up in autumn protects the soil over winter. In very cold districts, pull mulch back from small trees in winter so frost can't build up around them on still nights.
Common questions
Does wood mulch rob nitrogen? Only in the thin layer where mulch touches soil, as it starts to break down. It doesn't affect the tree's roots below. Don't dig wood chips into the soil, though.
Does mulch attract termites? Mulch itself rarely causes problems, but keep it away from house foundations and timber structures.
Record when and what you mulched with in Trees n Bees, along with what it cost. Your soil tests line up year on year with the compost and mulch added in between, so you can see whether the soil is improving.