A persistent problem; No garden can escape them - weeds. Hannah Stephenson looks at a new book to help gardeners fight the annual problem.

ANNUAL weeds are already springing up in my flowerbeds, but it's the persistent perennial weeds that cause the most problems.

While bindweed snakes its way through borders and up hedges, ground elder is emerging from under my neighbour's fence and couch grass is appearing amid perennials and shrubs.

In the past I've taken to zapping these difficult perennial nuisances with systemic weedkiller, but if you don't want to go down the chemical route, is there any other way to get rid of these invasive weeds? "There is no easy solution to perennial weeds, but you can make your life slightly easier by containing the problem," says plant ecologist Ken Thompson, senior lecturer at the University of Sheffield and author of The Book Of Weeds.

"Assuming that the bindweed, or whatever, is confined to part of your garden, make sure it stays there. Do not inadvertently move it around with other plants, or in soil or compost.

"The worst perennial weeds can spread metres in one season, so the time to act is now," Thompson says.

Persistent weeds require persistent action.

"Rotavating the whole area generally makes it worse -

every bit of root or rhizome will grow into a new plant," he warns.

Ground elder will be weakened with persistent hoeing, but that won't kill it.

The rhizomes are shallow, so digging them out is possible, although it tends to creep among other plants, which makes digging difficult.

It is possible to dig out the rhizomes of couch grass, but use a fork, loosening the soil as you go, to pull out long, intact lengths of rhizome.

Perennial nettle rhizomes are shallow and not very brittle, so can be dug out with a fork. Pearlwort is almost impossible to hand pull because bits of stem and root are always left behind.

However, as it is so small, it can be controlled through mulching and by filling vacant space with other plants.

Perennial weeds usually pop up among flowers and shrubs, so hoeing is often not possible. If you pull up the weeds you'll always leave some shoots behind and even when you dig out as much root as you can, it generally won't eliminate the problem.

"The only long-term solution is to remove everything - garden plants and weeds - from a bed or border and start again with clean soil," says Thompson.

It sounds drastic and it is.

You can try digging out every piece of weed root and rhizome as soon as you see any growth appearing, or you can cover the soil with a tough layer of old carpet to block out light and prevent weed growth. You'll need patience, as total eradication is likely to take at least a year.

If you need to remove ornamentals that you want to save, remove all traces of weed root among the roots and temporarily plant them elsewhere.

Once the area is weed-free, cover the bed with a permeable, weed-suppressing membrane and replant your saved plants through holes in it.

"Do not be tempted to cut corners by laying the anti-weed membrane over an existing perennial weed problem," warns Thompson.

"The weeds will find a way out through the planting holes and more vigorous weeds will even come through the membrane." Alternatively, you could put a thick layer of organic mulch such as compost or bark - at least 10cm (4in) - to prevent weed seedlings appearing.

. The Book Of Weeds, by Ken Thompson, is published by Dorling Kindersley, price pounds 12.99..

CAPTION(S):

FIGHTING BACK A flower bed is covered with a permeable, weed-suppressing membrane.