They are the bane of gardeners' lives - but there are ways to eradicate bindweed, ground elder and couch grass.
At this time of year, the toughest of invasive perennial weeds are doing their worst, smothering plants under the ground and strangling them above it as they climb relentlessly up anything with a stalk.
Here, we look at three of the worst culprits and what you can do about them.
1. Bindweed
Probably the most prevalent of weeds in the average garden is bindweed, a rampant strangler which twirls itself around prize plants and produces funnel-shaped white flowers of its own.
Never pull bindweed from the top or you will be in danger of pulling up the plant you are trying to save from its clutches. You need to follow its path down to the soil and pull it up from the base, with every last piece of root as you come across it.
However, the thick white roots are brittle and are likely to break if you try to dig them out, which then creates root cuttings. The best way to keep it in check is to catch it when the shoots first show through the ground and treat it with spot weedkiller.
If it is growing at the base of shrubs, it may help to pull off emerging stems at ground level every few days. Repeated applications of systemic weedkiller give the best chance of killing it.
If it is growing up plants, unravel the bindweed from them and then paint the exposed leaves on the ground with weedkiller.
2. Ground elder
This rampant, vigorous perennial weed spreads quickly between cultivated plants, forming clumps of green, lobed leaves and heads of creamy white flowers in summer, competing for nutrients and light with your favourite plants.
The only way to tackle it in established beds is to dig up your cultivated plants and carefully tease out the white roots of the ground elder. Just be warned that you need to remove every single white strand of root from the earth when you do dig the ground elder up.
And don't think that a rotavator will do the trick, because that just breaks up the many roots, it doesn't remove them, and will just exacerbate the problem because all those broken roots will start growing again.
You can also hoe regularly to sever the leaves from their roots, which will weaken the ground elder, but you will need to do this regularly over quite a long period of time if you hope to eradicate it.
If you must go down the chemical root, spray the leaves of the ground elder with systemic weedkiller during dry, still weather and re-apply during the season as soon as you see any regrowth. Wait until the leaves have completely wilted, then dig the whole lot up.
3. Couch grass
Couch grass just looks like thick blades of long grass with wiry stems, but dig deeper and you will find creeping white underground stems (rhizomes) with sharp points, which can extend underground for a considerable distance in all directions, producing new plants along the way.
Hoeing is useless and digging it out is difficult, particularly if it has invaded a shrub or perennial plant. In this case, the best course of action is to dig up the whole plant to enable you to tease out the couch grass roots from those of the plant you want to keep.
You can try forking out the roots on lighter soil, but if you leave any behind, it will regrow. If you opt for a systemic weedkiller, take care if your weeds are growing around desirable plants. In such cases, you can buy glyphosate in a gel formulation where application is by a small paintbrush.
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