weeds

Weeds are simply plants which are growing in the wrong place. They are usually the native plants which are best adapted to the environment where they grow; sometimes they have been introduced in the past for culinary, medicinal or decorative purposes. The seeds they produce can lie dormant in the soil for many years, germinating when it is cultivated, or imported with 'new' topsoil. Even in a "wild" garden the native plants must be controlled to give the more pleasing effect we seek.

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 and does not blow around so much, although it needs to be replenished sooner. The mulch is more effective if a membrane is laid first.

Laying a membrane alone is not very attractive, also as it is porous some light gets through which encourages germination of seeds and re-growth from remaining roots, so mulching on top should block this. Seeds from surrounding weeds and those blown in on the wind can germinate but will not be able to grow down and establish well.

A membrane is only a short-cut on beds if the perennial weeds have not been dealt with first as it prevents them from coming through for a while. They usually find their way to planting holes in the membrane and reappear, especially grasses. So the membrane solution is only temporary on borders and you may conclude from this that more time spent on preparation may be the better long term solution.

More economic mulches are home-made compost, grass clippings, old carpet, wetted newspaper (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.

Worms and birds turning over the mulch and removing the occasional weed will all cause the soil to rise to the surface. So 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 root-ball of that present may contain the seeds or roots of other weeds 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 root-ball and remove any roots not attached to the plant.