Warmer weather wakes them up, so wise up now to prevent them getting the upper hand, says Adrienne Wild

Many gardeners turn a blind eye to those beautiful yet promiscuous border plants like pot marigolds, granny’s bonnets and lupins, yet when roguish wild plants like dandelions, groundsel and stinging nettles behave similarly, they are despised for sucking the life out of prized vegetables and wreaking havoc in beloved flower beds.

They are blamed for stealing water and nutrients from the soil, robbing their neighbours of light and playing host to delinquent pests.

A sprig of ragwort

Ragwort © iStock

Know your enemy

A swift push of the hoe or a squirt of weedkiller might be considered the first line 
of attack to kill weeds, but this slapdash approach can be expensive, time-wasting, and damaging to wildlife. It’s far more effective to get to know them, understand what makes them tick, then find the best control.

Start by researching how your offending weeds grow and spread. Annuals like chickweed, groundsel and fat hen wake up and emerge in spring, develop quickly, flower then produce seeds and die all within a single year.

Cheeky ones like chickweed will sneak in several successive generations and can become a real problem on vegetable plots that are regularly disturbed and cultivated.

To stop them, adopt a ‘no-dig’ strategy and leave all your cultivating to earthworms. Cover bare soil with newspaper or black plastic and plant through slits in this, then mulch.

Routine hoeing when the seedlings are small can be effective for annual weeds, as can pulling them out by hand, and your haul can be put in the compost bin. Stick to the old adage, ‘pull when wet and hoe when dry’.

Beating biennials

Biennials, such as shepherd’s purse, hairy bittercress, teasels and ragwort, spread their life cycle over two growing seasons. First they produce a rosette of leaves and underground roots, which always sit dormant over winter.

The following season, they produce flowers and before they die away, set seeds, which will be ready to germinate the following spring.

These plants tend to colonise borders where permanent plants flourish and the soil is rarely cultivated. Chopping out the weeds and covering the ‘clean’ soil with a thick mulch of bark or decorative aggregate can be a useful control.

If the weeds are allowed to wilt for an hour you can add them to the compost bin, knowing they won’t re-infest the garden.

To kill weeds a daisy needs to be removed with its roots

Daisy © iStock

Persistent perennials

Watch out for nettles, bindweed, dock and couch grass, which start life from seed. Their searching, underground stems can easily invade from a neighbour’s 
plot, so keep your eyes peeled, especially because these weeds keep on going through the winter.

Normally the culprits are quick growers, so the best defence is to squeeze them out using stronger, ground-hugging varieties to starve them of light and suffocate them while they’re still struggling to get a foothold.

Covering the ground with a colourful and dense carpet of vegetation won’t just look good and prevent weeds becoming a nuisance, it will also provide a habitat for beneficial insects and other predators – so it’s a much better strategy than concrete or paving for creating a low-maintenance garden.

Excellent ground-cover plants are hostas, bergenia, epimediums, hellebores and brunnera, which all thrive in shade, and achillea, euphorbia, nepeta and stachys, which are well adapted to dry conditions.

To defeat perennial weeds, dig out and burn all traces of their roots. ‘Off with their heads’ works, too, as without flowers to produce seeds, they can’t spread far.

For persistent plants like nettles, ground elder and horsetail, have patience and cut plants down and dig out the new shoots every two or three weeks over several years to weaken them.

If you have to resort to using chemical weedkillers, one of the most effective is Roundup, which generally kills any plant it touches but won’t harm the soil.

It can also be painted on the leaves of weeds that are tangled up in border plants, to kill them off without affecting any precious plants growing around them.

Japanese knotweed - a common garden pest

Japanese knotweed © Alamy

Japanese knotweed

This herbaceous perennial was first introduced to Britain in 1825, and at the time was declared to be an outstanding garden plant. Today, it’s better known as a pernicious weed that’s virtually impossible to eradicate – even a tiny fragment of root in soil can grow again.

By law, it’s an offence to plant or cause the species to grow in the wild in the UK.

Its bamboo-like stems are capable of bursting through tarmac and concrete, and will grow 2.1m or more before they die for the winter. Its thick rhizomes spread underground in all directions and up to 2m deep to create an ever-expanding clump.

The best approach is to dig the plants out and cut back the emerging growth every two to three weeks over several years to weaken them. Then cover the ‘cleaned’ soil with a landscape mulching fabric to weaken the new shoots, which will struggle to survive due to lack of light.

On a large scale, call a specialist company to get rid of it.