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weeds, will travel

Top TV gardener Alan Titchmarsh offers tips on weeding out problems in the garden including the dreaded Japanese knotweed. By Hannah Stephenson


caught up with Alan Titchmarsh at the recent BBC Gardeners’ World Live show when he was giving advice on how to combat Japanese knotweed, the peril of many gardeners, a weed which is

right up there on the list of seemingly indestructible thugs. “It was brought into this country as an ornamental plant by the Victorians, who thought it was beautiful,” he lamented.

It has an underground network of tough, fast-growing rhizomes which makes it really difficult to control and in the summer the bamboo-like stems grow to more than 2.1m (7ft), suppressing all other growth. The RHS advises that if you’re going to try digging it out, remove as much root as possible, then repeatedly destroy regrowth. In this way the energy reserves in the remaining underground parts will be gradually exhausted but this process could take a very long time.

Another option is to place a layer of carpet over it but you’ll have to leave it a long time before it dies and you can dig it up. And when you dispose of the plant, do so carefully, allowing it to dry out before burning. Whatever you do, don’t put it on your compost heap or into your normal household waste because it colonises without seeding. It might be worth contacting your local council for advice on its disposal.

Titchmarsh says the best time to tackle this incessant weed is when it’s in flower. “Chop it down to ground level and when it starts to regenerate and particularly when it’s flowering, that’s the best time to spray Japanese knotweed,” he says. He says it’s more susceptible to systemic weedkillers such as Roundup later in the season. “Give it one big blast in autumn or late summer when it starts to flower,” he advises.

If it’s coming through from a neighbour’s garden, you’ll need to put a physical vertical barrier in the soil, digging a trench not less than 2m deep and inserting a tough, impenetrable membrane into it.

“My own nemesis is ground elder, introduced to Britain by the Romans as a pot herb and for its supposed medicinal purposes. I well recall when I first moved to my present house, one border was covered in it and I ended up putting weed-suppressing membrane

28 Life Begins Pampant pest ‘Yellow Couch Grass’

on the whole area, left it for about six months and then dug out every bit of root I could see. Since then, it has threatened to appear from my neighbour’s garden, but I spray emerging leaves with systemic weedkiller on warm days in spring and that seems to keep it at bay” he says, in his smooth and reassuring tones.

Persistent hoeing will weaken the plant but won’t kill it as the rhizomes are brittle and the plant will regrow from any fragment. If the weed creeps among your other garden plants, you may end up having to dig those up as well and untangle the runners from their roots, then allow time for any remaining bits to regrow and treat them with glyphosate.

Another rampant pest is couch grass, with its fast-growing rhizomes, which can produce hundreds of feet of roots underground, giving rise to a mass of shoots above ground. It makes plants look untidy, with long blades of grass sticking out among your flowers, but can be dug up as the roots are shallow, rarely more than 20cm (8in) deep. If you loosen the soil as you go, you may be able to pull out long, intact lengths of rhizome. Try not to leave bits of root in the soil because they will only come up again.

If your couch grass has spread from the lawn, create a clear edge between the lawn and flower beds to stop it spreading. Aggressive perennial weeds are a pain - but planning your attack and patience will hopefully help to eradicate them.

Matt Faber/PA Photos.

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