The Truth About WeedMAT — What Works, What Doesn't, and What's Quietly Ruining Nelson Gardens

By Roots & Rise Gardens and Design.

Every week in Nelson and Tasman, someone heads to the hardware store, grabs the cheapest roll of weedmat they can find, and comes home feeling like they've solved their garden problem once and for all.

They haven't.

This isn't a knock on anyone. It's just that weed matting is one of the most misunderstood products in the garden world. Used well, it's a genuinely useful tool. Used poorly — or with the wrong expectations — it creates more work than it saves.

Let's talk about what it actually is, what it actually does, and how to use it properly so your Nelson garden doesn't end up worse than when you started.

First, Reset Your Expectations for Weedmat

The number one mistake people make before a single staple goes into the ground is this: they think weed matting is a permanent solution.

It isn't.

Every single weed mat — no matter how expensive, no matter what it's made of — will eventually break down. The real question isn't if it breaks down. It's what it breaks down into.

Think of weed matting as giving your new planting a head start over the weeds. That's it. It buys time while your plants establish, fill out, and eventually shade out the competition themselves. It is not a forever fix. It is not a substitute for good prep, good planting, or good ongoing care.

With that mindset, it becomes a really useful tool. Without it, you'll be bitterly disappointed in about eighteen months.

The Problem With Plastic Weedmat

Walk into any garden centre in Nelson and the cheapest option on the shelf is almost always plastic weed matting. And yes, it works — for a while.

But here's the thing. When plastic weed matting breaks down, it doesn't just disappear. It leaves microplastic particles behind in your soil. Those particles don't go anywhere. They stay in the ground, in your garden, in the ecosystem you've spent time and money trying to nurture.

At Roots & Rise, we don't use plastic weed matting. We know it's the cheaper option. We choose not to use it anyway.

What We Use Instead: Coir Matting

Our preferred product is coir matting — woven coconut fibre. It's biodegradable, it's natural, and when it eventually breaks down, it actually feeds your soil rather than contaminating it.

Coir matting typically lasts up to five years when properly covered with mulch. In direct sunlight without coverage, it can break down in as little as 12–18 months — which is exactly why the bark mulch on top isn't optional, it's essential. The mulch protects the matting, extends its life, and does half the weed suppression work itself.

One thing worth knowing: coir matting provides good weed suppression while your plants are getting established, but some weeds will still push through over time. That's not a flaw — that's just the reality of working with natural materials. Plan for it, and you won't be caught off guard.

A note if you're shopping around: some coir products come reinforced with polypropylene for added strength. Check the label — these aren't 100% biodegradable due to the nylon content. If soil health matters to you, look for the fully natural fibre option.

Prep: The Step Most People Skip

Here's where most weed matting jobs go wrong before the matting even comes out of the bag.

Step one: knock down the weeds first. Line trim everything right down to the ground. Leave nothing to feed the plant. If you've got larger growth, pull it by hand. Get it as close to bare soil as you can.

Step two: consider a knockback spray. A light application of a desiccant like Weed Weapon helps to really knock back anything left at the surface. Give it a day to work before you put anything on top.

Step three: then lay your matting. Not before. After.

If there's a large weed or a thick stem and you're tempted to just throw the matting over the top of it — don't. It takes a few minutes to cut it down properly. A big bubble in your weed matting means a strong plant underneath with plenty of fight left in it. It will push through. You'll have to redo the whole job.

Step four: staple it down. This one surprises people. Before you put bark or aggregate on top, staple the matting into the ground so it doesn't shift. Pay particular attention to the edges and anywhere two pieces overlap — that overlap is your most vulnerable point.

The Overlap Problem

Speaking of overlaps — this is one of the most common installation mistakes we see.

If two pieces of matting meet with barely any overlap and no staples holding them together, you've just created a highway for weeds. They will find that gap. They will push straight through it.

Make your overlaps generous. Staple them down properly. Don't skip this step.

And one more thing: if your matting comes folded — double-check before you unfold it. Some matting is sold pre-folded because it's meant to be laid double-thickness. Unfolding it and using it as a single layer cuts its effectiveness dramatically. Read the instructions before you start, not after you've laid the whole garden bed.

What Goes On Top — And How Much

Not all mulch is equal. In Nelson we're actually quite fortunate — there's a good range of options available locally.

You'll see decorative bark cubes, coloured mulches, river rock, and all sorts of other options at garden centres. Our honest recommendation? Forest floor mulch. It's the most affordable option, it decomposes beautifully, and it's absolutely teeming with mycorrhizal activity — which feeds your soil and promotes healthy plant growth over time. Fancy isn't always better. Sometimes the cheapest option genuinely is the best one.

A word on river rock: it looks great at first. Clean, tidy, no weeds in sight. And then organic material starts settling between the stones. Seeds blow in. Weeds take hold. And suddenly you're weeding through rock aggregate in the height of a Nelson summer — by hand, in 30-degree heat, because you can't get a tool in between the stones. Zero out of ten. Do not recommend.

How deep does the mulch need to be? Deeper than you think. Aim for around 10 centimetres — roughly four inches. Research backs this up: for new beds or areas with significant weed pressure, four to six inches is the recommended depth. The thickness serves two purposes: it suppresses light so weed seeds can't germinate, and it adds weight to hold the matting in place. A thin skiff does neither.

One bonus of good mulch coverage: it can reduce evaporation from your soil by up to 70% — genuinely important in New Zealand's sunniest region over summer.

When Weed Matting Isn't the Answer

There are gardens where we'd actually talk you out of weed matting altogether.

If you've got an established garden with existing plants that are just a bit sparse and weedy between them — matting is going to be a nightmare to install and won't really solve the underlying issue. The better solution is to fill in the gaps intentionally.

Plants compete with each other. When you leave space between your intentional planting, weeds will fill it. The answer isn't to cover the gaps with matting — it's to fill those gaps with more of what you actually want.

We're currently working on a slope where the original ornamental grasses have grown beautifully to their full spread but there's still plenty of open ground between them. The plan is to interplant more of the same in a diagonal offset pattern — so the grasses eventually overlap, shade the soil, and outcompete anything that tries to come up. That's long-term weed suppression that doesn't rely on a product that's going to break down in five years.

When choosing what to plant, always look at the spread listed on the label and think about what that space is going to look like in five to ten years — not just right now. Plant dense enough that your intentional planting will eventually close the canopy and do the work for you.

The Weeds That Will Test You in Nelson

Nelson's growing season is relentless. We don't really get a proper winter here — things just keep growing, which is one of the great joys of living in this part of the world, and one of its great gardening challenges.

Two weeds in particular are worth knowing about:

Old man's beard (Clematis vitalba) — if you've driven through the Tasman region in summer, you've seen it. It looks like it's snowing when it goes to seed in the height of summer, which is gutting to watch. It spreads everywhere. If you find it on your property, you don't always need to haul the whole vine down — find where it emerges from the ground and cut it there. Without its root connection, it'll die back.

Bindweed (Calystegia silvatica) — great bindweed, with its large white trumpet-shaped flowers, is one of the most frustrating weeds you'll encounter in a Nelson garden. If you have it, we're genuinely sorry. When digging it out, tease the soil gently — any fragment of that white root left behind will regrow from that point. Follow the root as deep as you can. Be patient. It will take multiple sessions.

At Roots & Rise we don't believe in destroying the soil ecology with harsh sprays just to take the easy route. So yes — tedious hand weeding it is. But your soil will thank you.

(Nelson weeds deserve their own full blog post — watch this space.)

The Bigger Picture

Every weed mat breaks down eventually. The choice you make is about what it leaves behind when it does.

We're stewards of this land. The small section of earth you own or tend — it matters. The choices you make in it matter. Not just for you, not just for right now, but for whoever comes after you. Future owners. Your kids. Your community.

The cheap route isn't always the best long-term route. And even if you won't be around to deal with the consequences in ten or fifty years — we'd like to think that matters to people anyway.

At Roots & Rise, we try to leave every space we work in better than we found it. That starts with the small decisions — like what goes under your bark mulch.

Roots & Rise Gardens and Design — Nelson Tasman rootandrisenz@gmail.com Serving Nelson, Richmond, Brightwater, Wakefield, Mapua and the wider Tasman region