Weeds

Weeding Paved Surfaces

It’s not a very exciting subject for gardeners, but almost everyone has a driveway, a small sidewalk or a paved or gravel patio. So how do you keep these spaces free of unwanted plants without using harmful herbicides?

Unfortunately, glyphosate is still too widespread: the world’s most widely used active substance, marketed under the Roundup brand by Bayer (formerly Monsanto), among others. Already in 2017, Marie-Monique Robin amply developed the situation in her book and documentary: Le Roundup face à ses juges. More recently, a 2021 report by INSERM (France’s national institute for health and scientific research) confirmed the increased risk of non-Hodgkin’s lymphoma. The report also pointed to glyphosate’s genotoxicity: a substance capable of causing genome and DNA dysfunction. Other risks mentioned included multiple myeloma and leukemia.

Low-Impact Non-Selective Herbicides

Fortunately, there are low-impact herbicides on the Canadian market, but beware: unlike glyphosate, these products only destroy the aerial part of the plant, not the roots. They are more effective on young shoots of annual plants, which have no root reserves and are therefore less likely to regrow. In any case, perseverance is required on established and perennial plants.

Low-impact, non-selective herbicides registered in Canada are readily available in retail outlets:

  • Mixtures of natural fatty acids (capric and pelargonic) are used to melt the waxy layer protecting the foliage from dehydration. This causes dehydration and death of the plant in about two hours.
  • Herbicidal soaps containing potassium salts of fatty acids. They can be used to control moss and lichen on roofs, wood framing, sidewalks and fences. Aren’t moss and lichen pretty?
  • Acetic acid is the ingredient found in dilute form (5%) in household vinegar. Commercial herbicides contain at least 10% acetic acid and are therefore more effective. They act in the same way as fatty acids, destroying undesirable vegetation non-selectively.

In any case, avoid spraying these herbicides near your flowerbeds or favourite plants, of course.

Thermal Weeding

But there are other ways of getting rid of unwanted plants on paved surfaces. Personally, I like the small propane torch. These can be found in large hardware stores or online for between $60 and $85. It looks like a cane: you just attach a small camping propane tank to it, which will probably last all summer, depending on the surface to be treated, of course. It’s not tiring, because you don’t have to bend over even to light it. Most models come with a built-in lighter. It’s always ready to use, and it’s even quite a zen activity. My partner loves doing it in the evening in our driveway!

Photo: Edith Smeesters.

For larger surfaces, there are models that can be used with a large cylinder like those used for barbecues.

Photo: Lee Valley.

Or there’s professional steam weeding equipment. For example, in 2022, the City of Salaberry-de-Valleyfield acquired a thermal weeding machine to eliminate weeds growing between paving stones and street edges. This device enables the Public Works Department to improve the efficiency of weeding operations on roadways and sidewalks. It’s both an economical and ecological solution: it replaces the use of noisy brush cutters or herbicides, even low-impact ones.

Photo: Salaberry-de-Valleyfield.

Of course, you can also simply use boiling water. This technique destroys the plant right down to the root, but watch your toes! I confess that the propane torch seems safer and always ready to use. But in any case, the operation should be repeated several times a year.

Photo: Edith Smeesters.

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Edith Smeesters is a biologist and a pioneer in ecological horticulture in Quebec. She has given countless conferences and workshops and written several books on the subject for over 20 years. She founded and has been president of several environmental organizations, such as Nature-Action Québec and the Coalition for Alternatives to Pesticides. She was a key figure in the creation of the Pesticide Management Code of Quebec, which has been in effect since 2003. She has received several awards for her involvement in the environment and is a member of the prestigious "Cercle des Phénix".

4 comments on “Weeding Paved Surfaces

  1. Maryl discuillo

    I absolutely totally and emphatically agree on the whole propane idea iIt adds to planet warming and toxic fumes I use horticultural vinegar and it works pretty well. And if there are weeds in the garden I just pull.by hand

  2. JUDY MARIE VILLENEUVE

    Plug your kettle outside close to you weeds. Vinegar acidifies soil so moss comes back easily and does suffocate small plants, it is unsightly and can be controlled by raising the ph with dolomite lime but takes a lot of it and is very slow to work.

  3. Although we are very fortunate to not need to contend with too many weeds relative to the area of the landscapes, some of the weeds that we contend with are impossible to kill, even by this technique. Ironically, in some situations here, weed abatement is important because of the associated fire hazard.

  4. Karen Rom

    Propane weed control continues the poison cycle, just in a different form: its ingredients are derived from fracking (which releases radon and other killer gases) and oil. In addition, using the propane torch spews toxic fumes into the air. Please say more about vinegar, and how do I get boiling water to my weeds. Safely. Love your usually down-to-earth help! Thank you.

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