Weeds are the bane of gardeners’ lives and are especially a problem on any bare areas of soil, such as veg beds, left empty over winter.
Weed-suppressing membranes act by blocking light and thereby preventing the germination of weed seeds. There are several types available, including woven black plastic (sold as Mypex and Groundtex), non-woven polypropylene which resembles thicker, dark-coloured horticultural fleece, and eco-friendly options made from paper, wool or jute. Some gardeners also turn to free options, such as old compost sacks or cardboard.
The Which? Gardening magazine researchers wanted to find out which ones would do the best job of keeping weeds at bay.
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Pros Effective, reusable with care Cons Contains plastic
Weedtex Non-woven Weed Control Fabric
Price from £16.45 for a 1 x 15-metre roll
Where to buy Ground Cover Solutions
Smart Garden G100 Anti-weed Fabric
Price from £14.99 for 15 sq m
Where to buy Garden Store Online
We tried Weedtex and Smart Garden G100 anti-weed fabric, both of which are made from bonded polypropylene fibres. Weedtex is a 50gsm black fabric; G100 is thicker at 100gsm. We found both easy to cut cleanly and to push black plastic fixing pins through. We also tried fixing the G100 with metal staples, but these caused the fabric to tear at the points where the staples go through. Both products kept weeds at bay, and the two plots had only 5% weed coverage at the end of May when weeds were growing strongly on bare soil. The thicker material warmed the soil by around 2°C above the temperature of bare soil. Both fabrics were intact at the end of the trial and could be reused.
Pros Very effective Cons Prone to shedding plastic threads
Groundtex Heavy Woven Weed Fabric
Price from £20.36 for 1 x 15-metre roll
Where to buy Ground Cover Solutions
Smart Garden G100 Woven Anti-weed Fabric
Groundtex and Smart Garden G100 Woven Anti-weed Fabric are made from strips of black polypropylene woven into a sheet of material, designed for a range of uses including under paving, gravel or decking. Both are easy to cut with strong scissors, but strands fray off cut edges, leaving strips of plastic in the garden that can get tangled round machinery. You need to cut slits in the material with a knife to push through the barbed plastic ground pegs or to plant through. Both products completely prevented weed germination and raised the temperature of the soil by a few degrees above bare soil temperature. They were durable and could easily be reused.
Pros Effective, reusable, environmentally friendly Cons Pricey
Price £89.99 for 1 x 25-metre roll
Where to buy eBay or direct from Hy-tex
This sturdy material looks similar to the non-woven polypropylene products we tried, but is made from renewable starchy vegetable matter and hemp fibres. It has a low carbon footprint and is fully compostable, leaving no synthetic residues. It was easy to cut and peg down and felt substantial and slightly woolly. The soil under the membrane remained moist and was 3°C warmer than bare soil. By the end of May there was a smattering of weed growth under the membrane, and the material itself didn’t show any deterioration so could be reused.
Pros Biodegradable Cons Not durable, tricky to use, rips easily
Price from £85 for a 1.22 x 30.5-metre roll
Where to buy Mulch Organic
Made from biodegradable paper that’s designed to rot down at the end of the growing season, this thick and rather rigid material proved tricky to use. The paper ripped in several places just three days after laying it, and we found that water pooled on the surface rather than draining through to the soil. It was held down with metal staples plus a border of soil, but this didn’t prevent it being blown away in the wind; we had to replace it three times during the trial after high winds and heavy rain. There was around 20% weed coverage on the plot at the end of the trial.
Pros Durable, eco-friendly, biodegradable, easy to use Cons Pricey, birds like it too
We really liked the look and feel of this product made from a jute backing topped with dense wool. We pinned it down with the suggested bamboo skewers, which were far smaller than they looked online - more cocktail stick than tent peg - but this didn’t matter as the wool felt melded itself to the soil and was unmoved by high winds. It did a pretty good job of keeping weeds at bay; we found only 15% coverage on the plot. Unfortunately, birds liked the wool, too, pecking off tufts to take away for nesting material. Even so the material was largely intact at the end of the trial. We think it would work well left in situ topped with compost to create new beds on areas of grass.
We also tried a jute weed-suppressing material supplied by Chimney Sheep and made from recycled coffee sacks. It was tough and hardwearing and, like the wool felt, is designed to degrade into the soil after a year or two so best left in situ rather than lifting for reuse.
Price Wool Felt £7.99 per linear metre (1.4 metres wide); Jute Mulch £140 for 1 x 25-metre roll
Where to buy Chimney Sheep
Pros Free Cons Difficult to use, not durable, unsightly
We tried old carpet, compost sacks and cardboard as methods for keeping down weeds. All three prevented weed growth but all had drawbacks. The compost sacks and cardboard were fiddly to pin down, requiring lots of overlapping and hence lots of pegs. Water pooled on the surface of the compost sacks, while the cardboard became sodden and started to disintegrate; it then blew around the garden once it had dried. Weighing it down with large stones or bricks would work better than pegs. If you can find offcuts of wool carpet without plastic, it makes a durable weed suppressant – but it isn’t that easy to come by. It was also a hiding place for slugs, as were the compost sacks. Our test of killing weeds without glyphosate found that cardboard topped with a 5cm layer of compost to weigh down the cardboard works well for clearing weedy ground.