Adrienne Wild explains how 11 of our most common weeds grow and spread, and how to eradicate them without using chemicals
Well-known for their painful sting, these weeds are widespread. They produce a dense mat of bright yellow roots and form thickets of erect stems more than a metre tall.
The green serrated leaves are covered with stinging hairs and brown tassel-like flowers appear from early summer onwards. While you may want to dig up and eradicate the weed with polythene and mulch, it’s useful to know that nettles are indicators of fertile ground.
Bindweed produces thread-like vines that wrap themselves tightly around plants, eventually strangling the life out of them.
It’s easy to recognise with its arrowhead-shaped leaves and beautiful white or pale pink trumpet blooms, but don’t be tempted to leave it alone because soon after the first flush of flowers are over you’ll be resenting it for taking over and ruining your garden.
It takes patience and willpower and several attempts to pull it up, as any fragment of root left behind will re-sprout. Cutting the vine back when it appears will weaken it and eventually cause it to die off.
A British native, shepherd’s purse has been used as a medicinal herb since ancient times. It was also used by soldiers on the First World War battlefields to stop bleeding. It’s a prolific weed, growing in sun or shade and on most soils.
From a rosette of hairy leaves, it sends up flowers on tall, wiry stems that are followed by purse-like pods, which hold up to a dozen seeds. Seed buried in the soil can remain viable for years, so aim to pull the weeds up before they flower.
A native annual, groundsel flowers and sets seed throughout the year. Even seeds that have been buried in soil for up to six months will germinate when exposed to light. It’s therefore important to grub out the weeds before the yellow flowers and fluffy seed heads appear.
Left to get a foothold, the leaves become host to rust fungus, which can spread to cultivated plants.
Chickweed produces several generations that grow, flower and produce seeds before dying. It can become a problem on vegetable plots, which are being disturbed and cultivated regularly, but is a good indicator of high potassium, nitrogen and lime levels and low phosphate, and one of the first weeds to wilt when the soil is dry.
Hoeing on dry days when the seedlings are small can be effective, while on wet days pulling weeds out by hand works best. Dispose of the plants as they re-root if left on moist soil.
Dandelion’s thick taproots delve deep into the soil and even in the cracks between paving, making them difficult to remove. If tiny pieces of roots remain after cultivating the soil, they will re-sprout and take over, so it’s best to dig them out with a fork, especially before the bright yellow daisy flowers turn into fluffy ‘clocks’ and release their airborne seeds.
A plastic sheet mulch will prevent dandelions getting a foothold, but you may find them useful for draining waste ground and make use of their edible vitamin-rich leaves in salads.
This edible weed is super-efficient. It is able to complete its life cycle in less than a month and disperse thousands of seeds from the spring-like seedpods. It grows anywhere and everywhere, from bare soil to walls, and is often imported in potted plants bought from garden centres, which can go on to infest an entire garden.
To control its spread it’s essential to pull up the young plants before they get a chance to flower and set seed. This occurs from March to August. Cultivating the soil will bring up new seeds, although mulching will help prevent them from germinating.
This is a troublesome annual weed, as the individual plants are capable of producing up to 20,000 seeds in its short lifetime.
It thrives on dry, cultivated soil, and seeds that have been buried for up to 40 years will germinate when exposed to light. The leaves are covered in a mealy white coating that glistens in the sun, which act as host for black bean aphid and may become infected with viruses, so it’s wise to keep it from establishing on the vegetable plot.
Owing to being covered by bristly hooked hairs, the stems and seeds of cleavers are sticky, which allows it to scramble around the garden and spread further afield by hitch-hiking on to animal fur and clothing. Seeds take just two months to become established plants, so in flower beds aim to grub them out as soon as the seedlings emerge and before they flower in mid-spring.
Mulching weed-free soil with a 5cm layer of composted bark will help to suppress seedlings.
This is a nightmare weed that produces a vast network of underground stems and roots that travel through the soil pushing up new shoots every 5-10cm along their length.
Keep your eyes peeled for the newly emerging tufts of grass throughout the year because instead of dying at the end of each season, these weeds keep on going through the winter and beyond.
Be vigilant, pulling up emerging shoots because any pieces remaining in the ground will re-sprout. To clear the weed without resorting to chemicals, cover the soil with thick black polythene for a couple of seasons to exclude light.
Although a bee-friendly plant, when the tall bamboo-like stems of Japanese knotweed emerge in spring they are capable of bursting through tarmac and concrete. Below ground, this indestructible thug gets busy producing thick, woody rhizomes that spread quickly in all directions.
Even tiny fragments that break off can grow again making it almost impossible to eradicate. By law, it is therefore an offence to plant or otherwise cause Japanese knotweed to grow in the wild in the UK. Even dumping contaminated soil and garden waste at the tip is a serious risk – so beware!