Weed Prevention

Weeds   Weed Removal   Weedkillers

Invasive Garden Plants   Weed Seedlings   Herbal Remedies   Weeds as Food

"Sweet flowers are slow and weeds make haste." - William Shakespeare

The most important time to prevent weeds is in the spring as the seed germinate to produce the new season's crop. The ephemeral weeds can mature very quickly and produce more seed. Also the roots of ornamental plants entangled with perennial weeds have not yet started into growth so can be dug up and the offending roots removed to prevent their spread.
To maintain a weed-free flowerbed you can use a mulch of bark chips or gravel. The former is best in a ground and composted form as it settles better blocking out light, does not blow around so much and is less likely to be scattered around by foraging birds, although it needs to be replenished sooner. Ensure the ground is weed-free and well watered before applying any mulch.
The mulch can be more effective if a weed membrane is laid first. Laying a membrane alone is not very attractive, so a mulch on top improves the look and keeps it in place. When using gravel the membrane keeps it separated from the soil as it will gradually sink by action of the footfall, rain and worms - it sinks even quicker on a path if laid on soil. Seeds from surrounding weeds and those blown in on the wind, can germinate but will not be able to grow down and establish well, and are easily removed from the loose mulch. It is important to remove dead leaves and debris from gravel as it decomposes to form a perfect medium for incoming seeds. There is a new type of membrane on the market which has fine particles of copper impregnated in the fibres and the claim is that it will prevent the germination of seeds. However the amount of copper appears to be quite small so as its action requires it to be converted to soluble salts, the protection may be short-lived as the copper dissolves away. Another claim is that it will deter slugs and snails if laid around vulnerable plants though it would have to be left exposed to ensure contact.
In the vegetable garden covering beds which are not in use with a thick mulch of compost or well-rotted manure will prepare them for the next crop and prevent germination of weed seeds. Alternatively weed membrane will keep the area clear; use small boulders or bricks to weigh it down.
A membrane should be omitted on a herbaceous border to allow the plants to develop more naturally and if you want to plant bulbs.
A membrane is only a short-cut on beds if the perennial weeds have not been dealt with first. It prevents them from coming through if it is continuous, but if there are plants dotted through it, creeping underground stems find their way to planting holes and reappear, especially the grasses. So the membrane solution can be only temporary on borders and you may conclude from this that more time spent on preparation is the better long term solution, with a mulch used to prevent germination of seeds in the disturbed soil. No amount of organic mulch will prevent persistant rhizomatous plants from coming through, eg. Bindweed, Couchgrass, Ground-elder, Horsetail and Japanese Knotweed will reappear and thrive. If weeds are allowed to thrive nearby they will re-infest the cleared area, also wind-borne seeds will always return, eg. Dandelion, Willoherbs or Thistles.
Apply the mulch as soon as possible after any cultivation of the soil which would have brought dormant seeds to the surface. The exposure to light will stimulate them to germinate. If the soil is left uncovered for a day or two they may not be visible when the mulch is applied, but after about a week the shoots will appear through the mulch, so any advantage is lost. Treating the area with a weed burner would damage surface seeds that might be about to germinate, before application of the mulch.

More economic mulches are home-made compost, grass clippings, old carpet, wetted newspaper or cardboard (a layer under a mulch will mean that it can be laid on more thinly so it goes further) or a combination of these. The plastic bags used for bark mulches and composts are usually black inside so they can be opened up and used as a barrier under the mulch but must be stabbed with a fork in places to allow drainage and to let water through to the plants. Any mulch must be at least 50mm deep, but be careful around the base of plants as it can cause them to rot off if it smothers the base of the stem.
Garden compost may contain weed seeds unless great care is taken with the material used to make it or the temperature it reaches during processing is sufficient to kill them. The grindings from a garden shredder can be composted separately and will make a perfect mulch as they should be free from seeds - avoid Buddleja, Hypericium or other shoots with mature seedheads. Grass clippings usually have a supply of Annual Meadow Grass seeds, also Clover and Creeping Buttercup, unless you have the perfect lawn.

Worms and birds turning over the mulch, and removing the occasional weed will all cause the soil to rise to the surface. Cats and wild rabbits also scrape the mulch about to bury faeces and search for roots - strange hairy fungi often sprout from buried cat deposits. Buried seeds will germinate if the mulch is not topped up occasionally. Also when planting into a mulched area move the mulch to one side first and replace after planting, topping up if necessary. Of course hoeing is also out of the question.

When planting potted specimens remove the top layer of the compost as this will probably contain seeds or spores picked up as they sat around at the garden centre. Also beware of gardeners bearing gifts, the rootball of that present may contain the seeds or roots of a pernicious weed such as Ground-elder, Bindweed, Lesser Celandine or Vetch and you'll spend the next few years trying to get rid of them! One option is to quarantine the plant for a while in a container to see if anything develops, or if it is the dormant season, wash all of the soil from the rootball and remove any roots not attached to the plant. This can also be a problem with plants sold at fairs and open days which have been dug up and potted for the day - sometimes they can be a bonus plant so if not sure, pot up the seedling or root and see what develops.

Weed roots invading from adjoining ground can be deterred with a barrier of thick plastic buried vertically to a depth of 30 to 40cm and protruding above soil level by at least 10 cm (disguise it with a row of stones or gravel-board). 50cm wide damp-proofing coarse plastic used by the building trade is ideal. Any joints should be formed by rolling the two pieces tightly, rather than overlapped. Other barrier materials such as sheet metal can be used, but it is more difficult to make them continuous - the roots can penetrate the tiniest gap and will travel along overlaps.
This is best done at the outset when preparing the plot, but can be done later as a remedial treatment. Care should be taken when digging close to the barrier as the smallest hole will allow the roots to come through - treat it like a pond liner and keep sharp objects away from it.
Landowners have an obligation under the Weeds Act 1959 to prevent certain weeds from invading adjoining property and could be prosecuted, plus have to pay compensation for allowing them to do so. (Somebody should tell the Roads Service which allows Thistles and Ragwort to dispense their seeds in the draught of passing vehicles!)

Try to keep weedy grass verges which adjoin paths regularly trimmed to remove any flowers or seedheads. Cutting the edges of lawns prevents the coarser grasses which tend to have creeping roots from invading adjoining flowerbeds and paths. The the grass should also be at least 75mm above the level of the bed to prevent the roots from migrating - this can be achieved by digging a gully. Alternatively install a solid mowing strip along the edge - a vertical edge of 'log roll' is not usually satisfactory as the grass grows through the gaps and cannot be cut with a line trimmer.

Weeds   Weed Removal   Weedkillers

Invasive Garden Plants   Weed Seedlings   Herbal Remedies   Weeds as Food

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