Yes, laying bark mulch over a weed mat is absolutely a DIY-friendly job — no licensed trades required, no building consent needed, and no specialist tools. With a bit of preparation and the right materials, most Kiwi homeowners can get great results in a weekend. Here's everything you need to know to do it properly.
Why Use Weed Mat and Bark Mulch Together?
Weed mat (also called landscape fabric or geotextile fabric) acts as a physical barrier that suppresses weed growth from below. Bark mulch laid on top adds a second layer of weed suppression, retains soil moisture, moderates soil temperature, and gives your garden beds a tidy, finished look. Together, they're one of the most effective and low-maintenance garden bed systems available.
In New Zealand's variable climate — from the humid north to the drier, frostier south — mulching also helps protect plant roots from temperature extremes and reduces how often you need to water during dry summers.
What You'll Need
- Weed mat / landscape fabric (available at Bunnings or Mitre 10)
- Landscape staples or pegs to secure the mat
- Bark mulch — pine bark, wood chip, or decorative bark (sold by the bag or bulk cubic metre)
- Scissors or a utility knife
- Rake and spade
- Wheelbarrow (for larger areas)
- Gloves and safety glasses when cutting or handling materials
Step-by-Step: How to Lay Weed Mat and Bark Mulch
1. Prepare the Garden Bed
Start by removing all existing weeds — roots and all. Any perennial weeds like convolvulus or kikuyu left behind will eventually push through even good-quality weed mat. Loosen compacted soil lightly with a fork, and add any compost or slow-release fertiliser now, before the mat goes down, as it's very difficult to feed the soil once everything is covered.
2. Edge the Bed
Define your garden bed edges with timber, steel edging, or bricks. This keeps the mulch contained and gives a clean finish.
3. Lay the Weed Mat
Unroll the weed mat across the bed, overlapping joins by at least 150–200 mm to prevent weeds sneaking through gaps. Cut around existing plants carefully, making an X-shaped slit rather than a large hole to minimise exposed soil. Secure the mat firmly with landscape staples every 300–500 mm along edges and joins — wind can lift unsecured mat quickly.
Tip: Choose a woven or non-woven geotextile fabric rather than thin plastic sheeting. Geotextile allows water and air to pass through to plant roots, whereas plastic can cause waterlogging and root suffocation.
4. Apply the Bark Mulch
Spread bark mulch evenly over the weed mat using a rake. The recommended depth is 75–100 mm — enough to suppress weeds and retain moisture without smothering plant crowns. Keep mulch 50–75 mm away from the base of shrubs and trees to prevent collar rot, which is a common issue in wetter NZ regions.
For a standard garden bed, a rough guide is:
| Area | Mulch Depth | Approximate Volume Needed |
|---|---|---|
| 10 m² | 75 mm | ~0.75 m³ |
| 10 m² | 100 mm | ~1.0 m³ |
| 20 m² | 75 mm | ~1.5 m³ |
Bulk mulch by the cubic metre from a landscape supplier is generally much better value than bags for areas over 10 m².
5. Water In
Once laid, give the bed a good water to help settle the mulch and activate any moisture-retention benefits.
Common Mistakes to Avoid
- Skipping weed removal first — the most common reason weed mat fails
- Overlapping joins too little — weeds will find every gap
- Laying mulch too thin — less than 50 mm provides minimal weed suppression
- Piling mulch against plant stems — this causes rot and pest harbourage
- Using black plastic instead of geotextile — it blocks water and air, harming soil health
- Not topping up mulch — bark breaks down over time (usually every 1–2 years in NZ conditions), so plan to refresh the layer periodically
Choosing the Right Bark Mulch
NZ garden centres and landscape suppliers typically stock several types:
- Pine bark — long-lasting, slow to break down, widely available
- Wood chip — breaks down faster, adds organic matter to soil
- Decorative bark — dyed or coloured options for a polished look
- Coarse vs fine grade — coarser grades last longer and resist wind better; finer grades suit smaller beds
Check with your local landscape supplier about what's available in your region, as products vary around the country.
When to Call a Professional
For most homeowners, this is a manageable DIY project. However, consider hiring a qualified landscaper if:
- You have a large area (over 50–100 m²) where bulk delivery, machinery, or significant labour is involved
- Your garden has significant slope or drainage issues that need grading or retaining work first
- You're unsure about plant health or soil conditions and want expert advice
- You want a professionally finished result with edging, irrigation, or planting included
A qualified local landscaper can assess your site, recommend the right materials, and complete the job efficiently. You can find experienced landscapers in your area at tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
