How should weeds be controlled in our green and sensitive age?

Weeds are the native vegetation exercising their birthright.

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Years ago I grew so tired of hearing the definition of a weed as “a plant growing in the wrong place” that I decided to invent my own. I contended, more charitably, that a weed is “a plant whose potential has not yet been realised”. And in any event, the expression “wrong place” is just, well, wrong, because weeds are growing in exactly the right place. They are the native vegetation exercising their birthright. The garden plants we have introduced from alien environments and habitats are the “wrong” element. 

Small wonder then that weeds, adapted over evolutionary time to live in our soil, are generally the better competitors, and if we do nothing to control them our gardens will soon resemble meadows and our cultivated plants be no more. But how should weeds be controlled in our green and sensitive age, when avoiding environmental contamination is at the top of all our agendas? 

There are two weed control options – chemical and physical. Long gone are the days when chemical weed control meant long-term contamination of the environment and minimal regard for public health; albeit there are still some question marks over a few products, most notably glyphosate, which is without peer for the control of deep-rooted perennial weeds but according to some authorities may just possibly be carcinogenic. In 2017 the EU continued to grant approval for its garden use, but it remains to be seen how and if this will continue post-Brexit. 

There are, however, now several fairly effective weed killers – at least for annual weeds – derived from plant products, of which I find the best are those based on pelargonic acid, which is obtained from the oil in pelargoniums. I use them, but never forget that a plant origin is not necessarily a guarantee of low human toxicity: think of strychnine.

Mulching (which starves weeds of light) and hoeing (which decapitates them) are the two best known, effective and widely used non-chemical weed control methods. But perhaps the biggest weed problem comes now, in spring, when you will need a lot of mulch to deal with them all, and the soil is wet and so unsuitable for hoeing (which would merely transplant the weeds rather than behead them). It is too early and not warm enough for effective use of almost any kind of chemical, natural, organic or synthetic product. Yet if my garden is anything to go by, there are tiny forests of germinating weed seedlings in beds and borders everywhere. Hence, bring on the flame weeder. 

Using heat to control weeds is nothing new. I can remember as a child my father having a monstrous device that must have been left over from the Second World War and in the wrong hands could surely have laid waste to half of Derbyshire. There are now several much more modest devices fuelled by replaceable canisters of a propane/butane gas mixture that last for about two hours.  They have names such as “Weed Wand”, and when I first saw one I thought it little more than a toy. But now it is the first choice in my weed control armoury at this time of year. It is of minimal value for established perennial weeds or mature annuals. But for tiny seedlings in wet soil it is just ideal and will do more than enough to remind germinating shepherd’s purse, groundsel and chickweed that although they may be native species they have no place in the cultivated beds of our gardens.

This article appears in the 03 April 2020 issue of the New Statesman, Spring special

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