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Organic Gardening

It’s the height of the season, and everything in the garden is growing apace – especially the plants you didn’t put there. Gaby Bartai provides a timely guide to organic weed control

Know your enemy!

It pays to get to know your local weeds: arm yourself with a good plant identification book and acquaint yourself with their life-cycles and modi operandi. Crucially, learn to recognise weeds (and crops) at the seedling stage wherever possible, so that you don’t lose valuable time waiting for them to identify themselves as friend or foe.

Annual weeds germinate, grow, flower, set seed and die within a single year. Some, called ‘ephemeral’ weeds, complete their life-cycle in a matter of weeks and produce several generations a year. Biennial weeds flower, set seed and die in their second year. Annual and biennial weeds are a particular problem on ground that is regularly cultivated; you can reduce their numbers considerably if you adopt a no-dig approach.

Perennial weeds survive from year to year in various ways. Though many hedge their bets by also producing seed, they have a range of ‘vegetative’ methods of spreading, colonising new ground by extending the reach of their roots, rhizomes (underground stems), runners or bulbs. The roots and rhizomes of many perennial weeds are able to regrow even if the parent plant has been removed, and some can regenerate from a piece as short as 1cm (1⁄2in).

 

Carefull weeding
A hand-weeding tool will spare your fingers on heavy or stony soil

WEEDING BETWEEN THE LINES

Weeds can quickly swamp new plants
Annual weeds can quickly swamp young crops like these beetroot seedlings

It’s always better to get the bad news out of the way first. Organic gardening has no magic bullet for weed control, no answers in a bottle. There are no weedkillers approved for use in an organic garden (there are socalled ‘organic weedkillers’ on the market, but not in the big organic catalogues, which tells you all you need to know.

Their effectiveness is very limited, and the fact that they are made of natural substances doesn’t make them harmless to wildlife.) Where you need to remove weeds from an organic garden, there’s no getting away from it: there’s work involved. Now the good news: unlike its chemical counterpart, organic gardening doesn’t wait for a weed problem to come along.

The first line of defence is to ‘design out’ weeds and ‘design in’ effective weed prevention; the second is to take a proactive approach to weed control. And, unlike its chemical counterpart, which in its more extreme forms favours a scorched-earth policy, organic gardening takes a selective approach to its weeds.

Learning to discriminate between your weeds is the first step in moving beyond zero tolerance; you quickly discover that some can, in fact, be accommodated. Some are pretty, and can be reclassified as wild flowers; others are edible, and can be reclassified as crops. Some stay small and don’t take up much space or many nutrients; others provide valuable biomass for the compost heap. And the presence of some weeds is essential to ensure a biodiverse garden catering for the needs of local wildlife, including beneficial insects.

The use of weedkillers leads inexorably to the use of insecticides, as without any weeds there will be few natural predators. Wherever weeds aren’t interfering with your gardening, let them be. But no amount of positive spin can get around the fact that this leaves plenty of weeds you don’t want. The weeds in your garden are, by definition, perfectly suited to its soil and microclimate and best placed to exploit its resources; they are there by virtue of natural selection, unlike the introduced species you insist on trying to grow. Weeds will germinate faster, grow more sturdily, and outcompete your plants for space, light, water and nutrients.

They also detract from the garden’s appearance; they can harbour plant diseases, and their wildlife value is sadly not limited to beneficial species – they also provide a habitat for pests.

Weed prevention

Weeds are opportunists; they can – and will – exploit any available niche. The lesson here is obvious: you need to organise your garden and your gardening in ways that reduce the opportunities for weeds.

Cover crops

There is no such thing as bare fertile soil in nature, and if you leave ground vacant, weeds will quickly move in to fill the gap. If a plot will be empty for more than a couple of weeks, sow a green manure crop appropriate to the length of the ‘window’ and the time of year, or a cover crop of annual flowers. Where bare soil occurs beneath permanent planting – under shrubs, for instance – grow perennial ground cover plants. Failing all else, weeds can themselves serve as useful ground cover, protecting the soil from the elements, and you can treat a crop of annual weeds as a green manure – but it is essential to dig it in before it sets seed. This can be difficult to time across a range of weeds, but can work well if you have one dominant weed. Chickweed is particularly good, accumulating a range of nutrients in its foliage.

 

Mulching

Mulches are indispensable in an organic garden, and high on the list of their benefits is that they suppress weeds. Most loose mulches will not kill existing weeds, so the trick is to weed and then mulch immediately, thereby preventing the weeds from regrouping the moment you turn your back.

Mulches work by preventing light reaching weed seeds, and to a lesser extent by impeding the growth of any seedlings that do emerge, so the most effective are dense materials like leafmould, bark chips and compost.

The weed-suppressing effect of lighter materials like straw and grass clippings is limited, but these can usefully be combined with a weed-suppressing base layer of newspaper or cardboard. Used on their own, loose organic mulches need to be at least 5cm (2in) thick to be effective, and they need to be topped up regularly – how regularly depends on the material.

Be aware that mulches may themselves contain weed seeds. Cow manure, hay and garden compost are particularly suspect, so use these where you can deploy a hoe at the first sign of trouble.


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