Mulch is the highest-return job in a garden. A properly mulched bed loses far less water to evaporation, stays cooler at root level through an Auckland summer, and stops most weed seed from ever germinating because it never sees light.
The catch is depth. A thin scatter of bark looks tidy for a fortnight and does nothing — weeds push straight through it. Greensward NZ spreads mulch at 75–100mm, which is the depth where it starts genuinely working.
What's included
- Weeding and bed preparation before mulch goes down
- Re-cutting bed edges so mulch stays where it's put
- Mulch supplied and delivered at trade rates
- Spread evenly to 75–100mm, pulled back from plant stems
- Paths and drives swept clean afterwards
- Advice on the right mulch type for each bed
Choosing a mulch
Bark and wood chip are the workhorses — they last two to three years, look tidy, and are ideal for shrub beds and around trees. Composted bark fines break down faster but feed the soil as they go, which suits perennial and vegetable beds.
Pea straw is excellent for vegetable gardens but breaks down in a season and can bring weed seed with it. Pebble and scoria never break down, which sounds like an advantage until weeds seed into the gaps and you can't remove them without lifting the whole lot.
Fresh, uncomposted wood chip is worth avoiding on planted beds — as it decomposes it temporarily pulls nitrogen from the topsoil, and plants go yellow. It's fine on paths and around established trees.
Depth, and the collar rule
Below about 50mm, mulch doesn't block enough light to stop weed germination. At 75–100mm it does, and it holds soil moisture through dry spells well enough that many established gardens need no summer watering at all.
The one place mulch must be thin is against plant stems and tree trunks. Piled up against a trunk it keeps the bark permanently damp and invites collar rot. We pull mulch back to leave a clear ring around every stem.
Weed mat: usually not worth it
Weed mat under mulch sounds sensible and mostly isn't, on ornamental beds at least. Within a couple of years, organic matter builds up on top of the mat and weeds germinate in that layer instead, rooting straight through the fabric. Now they're harder to pull, and the mat blocks you from digging and planting.
For permanent gravel paths and driveways, where nothing will ever be planted, it earns its place. In a garden bed, 100mm of mulch topped up every couple of years does a better job.
Mulching — common questions
How much mulch do I need?
One cubic metre of mulch covers roughly 10–13 square metres at the 75–100mm depth needed to suppress weeds. So a 30m² garden bed needs around 2.5–3m³. We measure the beds and give you a firm figure on the quote.
How much does mulching cost in Auckland?
Mulching is quoted per project — the quote is free — and the price covers the mulch, delivery and spreading. It comes down to how many cubic metres the beds take and how far the barrow run is. Beds needing weeding and edge re-cutting first are quoted with that work included so there are no add-ons later.
How deep should mulch be?
75–100mm. Below about 50mm it lets enough light through for weed seed to germinate, which defeats the purpose. Keep it pulled back from plant stems and tree trunks though — mulch piled against bark holds moisture there and causes collar rot.
Should I put weed mat under the mulch?
Generally not in garden beds. Within a couple of years organic matter builds up on top of the fabric and weeds root into that layer and through the mat, making them harder to remove. Weed mat is worth using under permanent gravel paths and driveways where nothing will be planted.