Zero tolerance

Having a garden full of Japanese knotweed drove me from my north London home. When I moved in, the green spikes that were pushing up along the base of the fence — the weed had colonised the garden next door, long before — looked like ornamental bamboo.

How very contemporary, I thought. By the time I'd wised up, knotweed had spiked the entire garden like a spear-wielding Roman army. Take it as a lesson: if you are not sure what that pretty plant is that's popping up all over your garden, find out quick, and deal with it fast. If it's that promiscuous, it's likely to be a weed and it's sure to spell trouble.

'Get it wrong and you could be reinfesting your borders next year'

Ken Thompson, plant ecologist at Sheffield University, has helpfully written The Book of Weeds: How to Deal with Plants that Behave Badly, which provides a rogue's gallery of annoying annuals and persistent perennials, as well as battle plans that include preventative measures and direct attack.

It is vital to know the difference between an annual weed and a perennial, points out Thompson. Annuals can usually be pulled out by hand; perennials are tougher to eliminate and will need digging out, taking as much root as possible.

If you just chop them off, warns Thompson, like the nineheaded Hydra, the result will simply be more heads. An annual can go on the compost heap, provided it is all leaves and no seedheads; perennials must be burnt or bagged.

Get it wrong and you could be reinfesting your borders next year; just one scrap of bindweed root left in compost can quickly become a twirling colony of shrub stranglers.

Zero tolerance is the rule, if you don't want springtime weeds to settle in for summer, spreading by seed on the wind — or your socks, warns Thompson.

Goosegrass, for example, is the traily, sticky green stuff that is easy to pull out in handfuls — but it's just as easy, when you get bits of it stuck on your clothes, to unwittingly spread GAP Photos/Victoria Firmston the green seeds all over the garden.

Lawn and weeds go together, says Thompson, like bread and butter.

Plantain isn't just a kind of banana: it's the pesky little rosette that is flat enough to be mower-resistant and, if you don't dig it out with a sharp trowel — I've found an apple corer to be effective — will pop up everywhere, flinging flowering stems at you as well..

Annual weeds are comparatively easy to eliminate: nothing works so well as a trowel, a kneeling pad, and a persistent gardener on bended knees. Perennials are a tougher proposition. Thompson rightly frowns on herbicides but concedes that in the face of a sea of bindweed or horsetail, few organic gardeners would not consider resorting to glyphosate; one giant spritz on a still spring day — two might be necessary — should do the trick, and you can replant soon after.

You will, however, need to dig up other plants within the spritzing zone and replant them later; glyphosate does not discriminate.

Japanese knotweed, the thug of all garden thugs, could need (says the RHS) several sprays and three to four seasons to eradicate. The organic alternative to ground infested with perennial weeds is to keep it under wraps, using a weedsuppressing membrane that you slice into to form a cross, folding back the flaps, to allow for planting.

For weeds that push up through cracks in paving, flameweeders are the pros' choice of weapon. Not a full-sized flamethrower, but a longhandled one that is similar to the blowtorch you might use to caramelise a crème brûlée.

Your best line of defence? Weeds need space, water and light, so a good, dense cover of garden plants, says Thompson, will do most of your weed control for you.