For many New Zealanders, a beautiful garden is a labour of love. But when that love is constantly tested by invasive twitch, stubborn couch grass, and the relentless growth of gorse or dandelion, the dream can quickly turn into a chore.
In the landscaping supply world, there is one product that causes more debate than any other: weedmat. You’ve likely seen the thin, plastic rolls in supermarkets, and perhaps you’ve even heard the horror stories of “weeds growing on top anyway.”
At Gardenscape, we believe the problem isn’t the weedmat—it’s the quality and the installation. This authoritative guide will break down the technical side of professional weedmat, why the “non-woven” distinction is vital, and how to ensure your landscaping project remains a low-maintenance sanctuary for years to come.
Understanding the Terms: Weedmat vs. Geotextile
In a landscape yard, you’ll hear these terms used interchangeably, but there is a technical hierarchy to understand.
- Weedmat: A general consumer term for any fabric used to block weed growth.
- Geotextile: The professional engineering term for permeable fabrics used in soil.
When people talk about “bad weedmat,” they are usually referring to cheap, woven plastic. When we talk about “professional weedmat” at Gardenscape, we are almost always talking about non-woven geotextile fabric.
The Technical Edge: Why Non-Woven is Superior
If you are planning to cover your area with decorative stones, pebbles, or heavy mulch, the material you choose makes all the difference. In the New Zealand climate—with our high UV levels and periods of intense rainfall—non-woven fabric is the gold standard.
1. Needle-Punched Permeability
Non-woven weedmat is manufactured by bonding synthetic fibres together using a “needle-punch” process. This creates a felt-like texture. Unlike woven plastic (which has tiny holes that can easily clog with silt), non-woven fabric is highly permeable over its entire surface.
- The Result: Rainwater passes through instantly into the soil, but more importantly, oxygen reaches the roots of your trees. Woven mats can sometimes “seal” the soil, leading to “sour soil” (anaerobic conditions) that kills your expensive plants.
2. Friction and Stone Retention
Have you ever seen a gravel path on a slight slope where all the stones have slid to the bottom? This is common with woven mats because they are slippery.
- The Result: The “fuzz” on non-woven geotextile creates friction. It “grips” your Black Basalt or Riverstones, keeping them in place even during a typical Kiwi downpour.
3. No Fraying
Woven weedmat is made of long plastic strips. Once you cut a hole to plant a shrub, the edges begin to unspool and fray.
- The Result: You end up with ugly black plastic threads sticking out of your garden. Non-woven fabric can be cut in any direction and will never fray.
The Science of “Fines Migration” (Project Insurance)
The #1 reason to use professional-grade weedmat under stones isn’t actually for the weeds—it’s for separation.
In New Zealand, many of our subsoils are clay-based. Without a heavy-duty fabric, the weight of your decorative stones will eventually press them into the soft soil. Simultaneously, fine mud particles (the “fines”) migrate upwards through the stones.
- Without Weedmat: Within 18 months, your $1,000 investment in white pebbles is mixed with $0 worth of mud.
- With Weedmat: The fabric acts as a permanent filter. The stones stay on top, clean and bright, and the soil stays underneath.
Professional Installation: The “150mm Rule”
Even the best weedmat will fail if it is installed poorly. Follow these three “pro-rules” used by New Zealand’s top landscape contractors:
1. Clear the Deck
Do not simply lay weedmat over existing weeds. You must remove the top 50mm of turf and treat the area with a knockdown herbicide if necessary. Level the ground so the mat sits flush; any air pockets under the mat are “incubators” for new weed growth.
2. The Overlap
When joining two rolls of weedmat, you must have at least 150mm of overlap. If you join them edge-to-edge, weeds will find the gap. In areas with invasive grasses like Kikuyu, we recommend an overlap of 200mm.
3. Steel Staples vs. Plastic Pegs
In hard or clay-heavy NZ ground, plastic pegs often snap or “pop” out.
- The Pro Choice: Use 150mm Steel Ground Staples. These are U-shaped and “anchor” into the soil. We recommend 2 staples per square metre, and one every 500mm along the overlapping seams.
Dealing with the “Weeds on Top” Myth
The most common complaint is: “I put down weedmat and I still have weeds!”
Technically, these aren’t “under-weeds”; they are “over-weeds.” Windblown dust and seeds land on your mulch or bark. Over time, that bark breaks down into a thin layer of compost on top of your mat. The weedmat is doing its job (blocking the soil below), but it can’t stop a seed from growing in the mulch on top.
- The Fix: Use a high-quality decorative aggregate (stone) rather than bark if you want 100% weed suppression. If you prefer bark, ensure you use a “clean” mulch like Forest Floor and top it up every year to prevent it from becoming compost.
Buying Guide: What to Look For
When you visit Gardenscape, look for these technical specs to ensure you are getting pro-grade material:
- Weight (GSM): For garden beds under mulch, 60gsm – 80gsm is sufficient. For under stones or paths, you want 100gsm – 120gsm (often called “Landscape Pro”).
- UV Stabilisation: Ensure the product is UV-treated for New Zealand’s harsh sun. While it should be covered by mulch or stone, exposed edges need to resist “crumbing” into microplastics.
- Hydrophilic Treatment: Good fabrics are treated to pull water through them, rather than letting it bead on top.
Summary: Is it worth it?
In the world of New Zealand construction and land stabilisation, geotextiles are non-negotiable. Why should your backyard be any different?
Skipping weedmat or buying a cheap substitute is a gamble. For a small fraction of your total project cost, you are ensuring that your stones stay clean, your soil stays healthy, and your weekends stay free.
Build it once, build it right.
Ready to start your project?
Check out our range of Professional Grade Non-Woven Weedmat at Gardenscape. We deliver bulk rolls and accessories across the region, straight to your site.
