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Tips for using ground covers for weed control

03 July 2012

In this excerpt from his book Weeding Without Chemicals, Bob Flowerdew compares and contrasts different ground covers for killing weeds.

Using plastic sheeting for weed control
Black plastic sheeting also heats up the soil, increasing the rate of growth and breakdown of weeds

The slower but more effortless way of clearing ground is to kill the weeds by stopping them seeing any light. This can be with plastic sheet, groundcover fabric, cardboard and newspaper, old carpets, or what have you.

Simply cover the weeds and they turn yellow and die. They produce more shoots and leaves; these yellow and die, get eaten by the soil life and slowly the surface becomes covered in worm casts.

Find out how planting ground cover plants can also reduce the amount of weeds

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Preparing the ground area

It helps to have a perimeter trench a foot or so deep and wide into which the cover hangs; this prevents weeds near the edge of it surviving from outlying roots.

If any weeds find a hole and come through the covering they must be pulled or pushed back under and the spot repaired. (A stone or brick on top may do, or a newspaper placed underneath the covering and blocking the hole will work well.)

Read our guide to preparing the soil for spring planting


The best time to cover ground is from late winter, then the weeds die in the flush of spring and are soon incorporated. 

Muck or compost can be spread beforehand and will be incorporated simultaneously. Such covers can also be applied on top of flushes of weeds or over green manures and are much less effort than hoeing or digging them in.

Black plastic sheeting

Black plastic sheeting does not kill all weeds well unless it is thick enough to exclude all light. Hold it up to the sun, does it show through? If so, use a double or triple layer or lay the sheet on top of newspaper, cardboard or other light-excluding mulch.

It works well as it also heats up the soil, increasing the rate of growth and breakdown of weeds and it keeps the moisture in all the way to the surface, also promoting growth and breakdown.

However, the sheet can lift or blow about so it needs tying or weighting down carefully. I find giant pins made from bicycle spokes or cut out of wire coat hangers handy for pinning down such short-term coverings, but for wind resistance little beats holding it down with cast-iron guttering or scaffolding poles.

Plastic sheet on uneven ground pools rainwater and channels it to the lowest point, so it must be laid carefully with that in mind. You can reduce the problem, indeed utilise it, by laying plastic sheet over a raked level, or graded, loose mulch or soil, with depressions to guide the water to just where you want it. Or you can create depressions around plants and fit the plastic about them, then the water will be delivered to them.

White sheet plastic

This is sometimes used to throw up light onto the crops but it does keep the soil a tad cooler. White plastic controls weeds if it is opaque, though it is somewhat slower in action than black plastic, which cooks them at the same time.

Punctured or perforated plastic sheet

This allows water and some air to pass through, but, unfortunately, some weeds will find the holes. If you use two layers the perforations do not align and so it works better, or it can be laid over newspaper or cardboard or a loose mulch if only weak weeds are present.

Woven or felted ground-cover fabric

This is the stuff. Usually this is black, sometimes glossy, and not awfully pretty. However, it is quite acceptable in most productive areas and useful for lining cold frames, under paths and in areas full of pots.

Some are just woven, some are more of a fleece; in either case the heavier and thicker the grade the better. This can clear new ground of almost all established weeds – including even brambles and stinging nettles, though they will push it up unless well-fixed! Of course, such weeds need pre-treatment by removing the old top growth and giving the area a cut or two with a rough tough mower. But then, providing the edges are well fixed down, any weeds enclosed re-grow into the dark, are bent down and are killed off – even the toughest.

Laid on top of clean soil, it keeps it clear of weeds and, because the air and rain pass through, it keeps the soil apparently much healthier than under black plastic sheet. In ornamental areas it can be covered with thin layers of a coarse mulch, such as bark or gravel, to improve its appearance. This may make more labour in the long run, though, as these can allow weed seeds to germinate and grow if not well policed.

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Old carpet

I no longer recommend this as the ground-cover fabrics do the same job. However, old wool and cotton carpets laid upside down did make a good job of killing off most weeds or keeping an area weed free. They rot and are not a permanent solution unless covered with a loose mulch such as bark.

Half-natural half-artificial carpets, latex backed or foam backed should never be used as they break up leaving nasty bits, but they are handy for lining the floor, walls and even the ceiling of your garden shed, and using as floor covering for suppressing weeds in storage areas of the garden.

Nylon carpets are very good, though, as they last forever and can be cut into convenient paths and patches; these kill the weeds under them and can be moved as needed. When they get soil stuck on them or weeds grow on them you simply turn them over or hang them up and hose-wash them clean.

Cardboard and newspaper

These are free, breakdown eventually and need careful weighting or they blow, but they work well and may also be used as reinforcement against tough weeds under black plastic or ground-cover fabric and, usefully, under loose mulches such as compost or bark.

The paper or board layer is strong enough to stop many weeds pushing through but it eventually rots. Although it seems newspaper and corrugated cardboard are relatively clean and leave few problems once broken down, it’s safer to avoid using glossy, highly coloured cardboard or paper (such as magazines) as these have polluting ingredients.

Find out how to make leaf mould for to maintain borders and give your plants a boost

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The opinions expressed are those of the author and are not held by Saga unless specifically stated. The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.