Control weeds – quick guide to the basics

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Last updated August 2014

Weeds need not be a problem. You just have to know what to do, when, and how often, to beat them completely.
Weeds – know your enemy
Annual weeds and control
Perennial (long-lived) weeds and control
Paving, patios and drives – weed control
Completely overgrown areas – weed control
Mulching for weed control

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Spear & Jackson Traditional Stainless Steel Dutch Hoe from Tooled Up £22.95



Spear & Jackson Neverbend Carbon Dutch Hoe from Tooled Up £22.95

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Weeds – know your enemy

Some weeds re-grow from pieces of root; others grow from seeds which may be in the soil or brought on the wind or by birds. So that old saying about one year’s seeding meaning seven years’ weeding is no doubt right.

If you aren’t sure which plants are weeds, then try to identify them from the photos on Crocus’ website>.

There are lots of ways of dealing with weeds, but there’s always a place in every garden shed for a good sharp hoe – keep it sharp with a file.

See the range of hoes from our online garden centre or hoes from Crocus.co.uk

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Fast Action Roundup Weedkiller from Wickes £3.99



Westland Resolva Xtra Tough Weedkiller Ready to Use Spray 1L from Wickes £4.99

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Annual weeds and control

Annual weeds (eg groundsel, rose-bay willow-herb, chickweed) are those which produce seed in the same year that they began to grow. They produce many seeds that drop near the plant, or blow around, and if they land on bare soil, they are ready to grow during the next mild period of weather. Wherever you disturb the ground, or where moles, worms or rabbits do this for you, seeds of annuals will germinate once the growing conditions are right. The seed may land after the soil becomes bare, or have been buried and then returned close enough to the surface for light to trigger germination.

  • Control annual weeds by hoeing. This chops off the stems at ground level, and the roots cannot re-grow. Or control them by digging the ground over so that you bury the weeds on the surface.
  • Don’t let annual weeds grow large enough to flower and seed, otherwise you’ll have an even bigger problem later. If you don’t have time to hoe every week, at least remove the flowers, so that seeds cannot be produced on the plant. The flowers can sometimes continue to develop into seeds, so bag up the deadheads and bin them, or compost them if your heap gets hot enough.
  • Hoe weedy and bare areas every week to kill visible weeds and disturb just-germinated seeds below the surface. Newly germinated seedlings won’t survive this treatment unless there is a lot of rain.

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Perennial (long-lived) weeds and control

Perennials include couch (twitch), dandelion, dock, thistle, bindweed, horsetail, ground elder, and Japanese knotweed. These live from year to year and can send up new shoots from their roots, so they survive hoeing to begin with. But:

  • Hoeing off shoots cuts off new food supplies to the root.
  • If hoeing is continued weekly, the pieces of root will eventually become exhausted and unable to produce any more shoots
  • Also, there’s no need to pick up weeds after hoeing, unless they have flower heads (the flowers could still develop and produce seeds) or you want to do some work in the area.

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Paving, patios and drives – weed control

Weeds that grow in cracks are awkward to deal with, although after heavy rain it’s sometimes possible to tease out the plant with its roots.

Boiling water is one way to control these weeds – unlike using pesticides, you don’t have to wait for a dry spell, avoid windy days or worry about your children, pets, bees or other life. We boil a kettle and then direct the water onto the weed leaves and try and trickle some water down to the roots. It often needs repeat treatments to kill perennial roots, but each dousing kills leaves and weakens the roots.

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Completely overgrown areas – weed control

Mechanical solutions

  • Overgrown areas are best cut down to the ground first, using a billhook, scythe, rotary mower (hire a tough one) or brushcutter.
  • Then rake the debris off and dig over the soil with a spade or plough. A cultivator stirs the soil up rather than burying the original surface, but is also useful. Any of these methods gives you bare soil which is easier to hoe than a weedy patch.

Chemical solutions – herbicides

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Roundup Fast Action Ready to Use Weed Killer 1L 1.12kg from B & Q £2.00



Fast Action Roundup Weedkiller from Wickes £3.99

As an alternative to mechanical methods, clear the ground with a weedkiller.

  • First decide whether you have annual or perennial weeds – if unsure, assume that there are perennial weeds present.
  • Study the labels on weedkiller and make sure you choose one designed for the problem. Although there are numerous trade names, there are only a few actual chemicals – these are listed as the active ingredient(s).
  • The active ingredient named glyphosate (such as in Roundup) is taken up by the plant’s leaves so eventually the roots are killed. This takes a while, so take note of instructions on the label, especially about the ideal size of weed to be treated. It’s better for there to be several leaves on the weed so that more chemical can be taken up. But an old established plant may need several applications before it’s killed.
  • For small areas of weeds, or for spot control of a few weeds, buy a ready-to-use weedkiller in a spray container. Then there’s no mixing needed.
  • Do not mix weedkillers (or any other garden chemicals) in the kitchen. Weedkillers are, after all, designed to kill, so should not come near food or drink or your skin. Take a bucket of water outside so you have plenty for mixing, washing out the sprayer afterwards, and washing your gloves. Keep a pair of rubber gloves for use with chemicals, and store them in the shed or garage.
  • Do not spray in windy weather, otherwise you risk spray in your face and on your neighbour’s plants.

Residual weedkillers

An overgrown area contains a great deal of weed seed in the soil, which you can prevent from germinating for months and months by using a type of weedkiller called a residual. Various types prevent seeds germinating for a certain length of time, from a certain depth of soil. But if you disturb the soil, the weedkiller becomes ineffective.

If you intend to plant or sow in the area in the near future, make sure that the weedkiller is suitable. Some residuals must not be used around newly planted shrubs, or plants susceptible to damage, so read the label before buying and using.

Search our online garden centre for weedkillers, or look at Crocus’ website.

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Mulching for weed control

Most weed seed germinates when exposed to light – this means that only seed near to the soil’s surface will grow. A mulch makes the soil’s surface darker and suppresses weeds. But perennial weeds can still grow through this, so must be dug out, hoed off for a season or sprayed, before a mulch is applied.

  • At least a two-inch depth of organic material is essential to inhibit seed germination. Use well-rotted compost or bark chippings (such as from B & Q or Rolawn). Top up the layer each year with a small amount of material.
  • Some weeds will still appear, from seeds blown onto the top of the mulch, but these are easy to pull out. If your garden compost has not heated up enough, weed seeds could still be present and grow. If you think your compost heap won’t kill weed seeds, don’t put flowering weeds (or roots of dandelion, couch etc) onto the heap, but bin them (in the council’s garden waste bin if you have one).
  • An alternative mulch for a large area is old carpet, cardboard or thick black polythene (anchored down) which will suppress weeds, kill any already growing, and buy you some time until you can deal with the area. However, this does encourage slugs.
  • In areas already planted up, you could use sheets of Plantex (or similar rot-proof woven material that allows water though) beneath bark or compost mulch, to prevent worms from dragging the mulch into the soil.
  • Growing a mulch – another possibility is to plant a green mulch ie something that will spread but that will be easy to cut down/mow off or pull up when you want to use the area. Geranium sanguineum (a cranesbill) is one we use because it spreads quickly, is ornamental (evergreen and has spring flowers), but is easy to pull up and doesn’t self seed. Growing green manure is an extension of this idea, where you choose a plant that will help lock nutrients into the soil, and dig in the whole plant once you are ready to use an area. You need to choose leafy plants that will be easy to bury near the surface and that will decompose easily. Look under ‘green manure’ in catalogues to see what’s available. Crocus has a handy green manure comparison table of various plants suitable, some of which are sold by Thompson & Morgan, either listed under green manure seeds or specific names.

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