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Weeds – friend or foe?

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Self-seeded forget-me-nots (Myosotis spp.) soon start to colonise disturbed ground. In a few weeks there will be no bare soil.

Whilst acknowledging the inconvenience of weeds in a garden, award-winning gardening and environment author, John Walker, extolls their wider and more important value to our ecosystem in his latest book, Weeds. (Please see the offer at the end of this article)

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Weeds are amazing. When I stumble upon a clump of creeping thistle, its pink, honey-scented flowers smothered with butterflies, bees and hoverflies during summer, I can’t help but feel humbled. But when I find it pushing up between my potatoes, and carefully try to loosen the soil so I can gently tease out its fleshy roots, I’m both irritated and amazed at the same time: irritated that this tough perennial weed hasn’t yet been eradicated from my vegetable beds – and amazed that I thought it could be. Any plant that can send its roots deep into the soil and is able to grow into a whole new plant from the tiniest root fragment is, you have to admit, pretty amazing.

WHAT IS A WEED?

Among my potatoes is the last place I want creeping thistle, but just down the road, on a bare plot destined for building, there is a massive clump where some of the stems are taller than I am. Here this beautiful wild plant seems perfectly at home, as it truly is when growing along hedgerows and banks. In my vegetable beds, creeping thistle is a serious weed problem, while on wild, uncultivated ground it is growing where it ‘should’ be. As soon as any plant, wild or cultivated, begins growing where we don’t want it – in the ‘wrong’ place – it becomes a weed. Pushing up through a path, both this raspberry sucker and the great bindweed entwining it are weeds.

Pushing up through a path, both this raspberry sucker and the great bindweed entwining it are weeds.

JAPANESE KNOTWEED – FRIEND AND FOE?

One of the most serious of all weeds, Japanese knotweed, was first introduced to this country in 1825 as an outstanding and much-heralded garden plant. Today its spread is so serious that at least one local authority employs someone whose job is solely concerned with its eradication! This is just one of several plants that started out being grown in the ‘right’ place, but which over time have become notorious for growing where we really don’t want them. Japanese knotweed is one of the most amazing, useful and resilient weeds I know, yet it is also one of the most pernicious, but despite all its bad press and the fact that it can be an offence to grow or spread it, I feel it deserves a second look.

I visited a massive clump of Japanese knotweed whilst writing my book, Weeds. Pushing into its forest of stems, I stepped into another world. I was surrounded by the buzz of insects feeding on its nectar-rich flowers, while below me was a carpet of brown, hollow stems, with spiders and other insects scurrying over them. I was once served some young, cooked shoots of this weed, which look similar to asparagus. They had a pleasant, slightly acidic flavour and were certainly a talking point. The young shoots are also a good substitute for rhubarb in jam and pies.

Killed by weedkiller, these tough dry Japanese knotweed stems are helping another weed – great bindweed – to thrive.

THE ‘HEALING’ ROLE OF WEEDS

Bare, exposed soil isn’t part of nature’s master plan. How many examples can you think of where soil is naturally found bare and with no plants at all growing in it? Good examples are beneath freshly uprooted trees, landslips, or where the ground has been charred following a heathland fire. However, bare soil isn’t bare for long; within days seedlings begin to appear and cover the ground with a miniature green forest. In a few months’ time the scar is barely noticeable. A year later you would never know it had been there at all.

Contrast these natural examples of bare soil with those created by man: ploughed fields and freshly dug gardens and allotments are obvious examples. But, left to nature, even these soon turn green. Think of those wild, overgrown allotments or that jungle-like abandoned garden – these too were once bare earth. We are constantly battling to stop weeds from growing, but all we are doing is keeping the healing powers of nature at bay.

WEEDS AND WILDLIFE

Some gardens and allotments might look neat, tidy and well-kept, but when you look closer, the air is empty of insects, there might be fewer birds around and wildlife in general is very much at a premium. Of course it’s true that you can grow cultivated ‘garden’ plants to attract wildlife, especially insects, into your garden, but it’s the naturally occurring weeds growing wild and free that really make the difference. This is because they have always been there. It’s their patch – they’ve evolved and adapted over time to make the best of the specific growing conditions around them. Wild animals and insects have evolved alongside them and they depend on each other.

Beneath the current year’s shoots is a dense mat of old, hollow stems used by overwintering insects.

Weeds act like a kind of living ‘plaster’ whenever soil is exposed. As far as nature goes, bare soil is out. When soil is exposed to sunlight it’s not only the earthworms that quickly burrow back into the darkness. Millions of microscopic soil organisms are also exposed to the potentially harmful rays of the sun, so the sooner plant growth covers the soil over again, the better. Once you appreciate this perfectly natural reaction by nature, you start to see that weeds aren’t there to deliberately frustrate our gardening efforts; they are simply doing their job. Just as new skin forms after we’ve caught ourselves on a rose thorn, weeds help heal wounds in the earth. Look at it another way: it’s us who are causing the problem by insisting on bare, neat-looking soil – open wounds, if you like.

FERTILITY BUILDERS

Left to their own devices, weeds help to improve the fertility of the soil in several ways. Their roots bind the soil together, helping to improve its structure and create a more stable environment in which soil life can flourish. Weeds with a deep taproot, such as curled dock, draw up plant nutrients from deeper in the ground, making them available to plants growing near the soil surface. Above ground, the stems of weeds help trap fallen leaves and other organic matter, which break down into the soil or are dragged underground by earthworms. And when the weeds finally die both the leafy tops and the roots decompose into valuable humus.

Nettles do no harm (apart from the odd sting) and can be cut regularly, then added to the top of the compost bin to help break down organic matter and add valuable plant nutrients.

As the soil becomes more fertile, different kinds of plants start to replace the ‘pioneering’ weeds. In the UK a typical succession might see shrubs ousting the pioneers by gradually shading them out, followed in turn by trees pushing up through the shrubs, finally shading them out too. The leaves that fall from the shrubs and trees carry on the job of building soil fertility begun by those very first weeds that sprang up on the bare soil. Then, when one of these mature trees is uprooted in a storm, ripping open a wound of bare soil in the earth, the whole process starts again.

In our gardens and allotments we buck this natural route to fertility by actively discouraging weeds and adding goodness in the form of garden compost, manure or natural fertilisers. This isn’t to say that certain weeds, such as perennial stinging nettle, cannot be used as part of an overall fertility-building plan for your garden. In fact, virtually all weeds ‒ even the most pernicious, like great bindweed ‒ can be put to good use. For me, working with weeds ‒ realising then releasing their potential ‒ is one of the basic tenets of an organic approach.

A good sign: sun spurge indicates a fertile soil rich in plant nutrients.

‘READING’ WEEDS

Most weeds, like most garden plants, do well in a slightly acid to neutral soil with a pH of 6.5–7.0, while others only thrive in very specific soil conditions and are often called ‘indicator’ weeds. These give clues to what type of soil we have, as well as to factors such as how well or badly drained it is, or how the ground might have been treated in the past. If you find sheep’s sorrel, the soil will be quite acid; creeping buttercup thrives in moist, poorly-drained soil, while patches of pineapple weed indicate hard, well-trodden ground. The presence of some weeds is a good sign: chickweed, borage, redshank and sun spurge are all signs of a fertile soil. Weeds like these can cause you future headaches, because as you get your garden into shape and start to boost soil fertility they are ready and waiting to move in.

Letting weeds grow on a bare patch of soil gives an insight into the condition of your soil and helps you learn to identify them as seedlings.

READER OFFER BUY WEEDS AND SAVE

This is an extract from the new and updated edition of Weeds: An Organic, Earth-friendly Guide to Their Identification, Use and Control (ISBN 9780993268342) by Kew-trained and award-winning gardening and environment writer and author, John Walker. This accessible, illustrated guide has over 100 full colour photographs. It’s fresh approach encourages you to see weeds as more than just unwelcome invaders in your flower borders, kitchen garden, allotment, greenhouse, polytunnel, patio, courtyard, containers, lawn, path or drive. It’s packed with no-weedkiller-required tips and techniques, helps you identify 60 common weeds, and explains how to clear weedy ground without doing any back-breaking digging.

Weeds is published by Earth-friendly Books at £15, but Home Farmer readers can buy a copy direct from Earth-friendly Books for just £14 (plus £3 postage and packing). To order Weeds, visit www.earthfriendlygardener.net/HF1 and follow the instructions. Please note that this offer is only available online.

The images used in both this article and the book are by Colin Leftley and John Walker.

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