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The ecologically responsible gardener – Controlling weeds

Dandelion (taraxacum) © cc Flickr (Simon-And-You)
The ecologically responsible gardener – Controlling weeds

Eliminating weeds is part of the daily routine for the ecologically responsible gardener. These plants seem to always find a way to grow just where you don’t want them. And what’s more, they absorb a portion of the soil’s nutrients that our flowers and vegetables need. But how to get rid of them without disturbing the garden?

Food for thought: Herbicides

Herbicides don’t only kill undesirable plants; they can also be harmful to other living organisms. Herbicides can be:

  • irritants,
  • harmful to aquatic species,
  • and even carcinogenic.

It is therefore important to be cautious—especially as most weeds can be eliminated without resorting to herbicides.

A few tips

Whatever method you choose, remember that:

  • weeds can wither away in the absence of light;
  • they should be eliminated before they can produce seeds.

Techniques

Manual weeding

The best way to get rid of a weed is to pull it up by hand with as many roots as possible, which is easiest when the soil is damp and crumbly. Dandelion weeders — steel claws on the end of a long handle — are very effective for removing weeds that form a rosette of leaves (e.g. dandelion, plantain).

Stale seedbed

This technique consists of preparing the soil and allowing weeds to germinate, then destroying them before sowing or planting. For good results, prepare the soil a few weeks ahead, when the weather is warm and humid. You can even water the bed and cover it with clear plastic to stimulate the weeds’ germination. Remove the weeds by hoeing, then sow the plants you want to grow.

Physical barrier

Metal or plastic edging can control some weeds that spread via subterranean stems (rhizomes). To be effective, the barrier must go down 15–20 cm into the ground.

Mulch

A good layer of organic mulch can inhibit the growth of weeds. Avoid covering the crown of plants and weed the bed before you put on the mulch. Pull weeds up manually when they come through the mulch.

Hoeing

Hoeing regularly is useful for eliminating weeds. Ideally, hoe your garden on a sunny day, when the soil surface is dry, so the weeds can’t take root again. Avoid hoeing too often, as this can dry out the soil. Watch out for the roots of your vegetables and ornamental plants.

Heat treatment

Devices known as flame weeders can be used to burn weeds growing between paving stones or on the edge of the sidewalk. No need to completely incinerate them.Pass the flame over the weed until it loses colour without turning brown. This method is effective on young annuals; perennials may require several interventions. It can also be used to destroy weeds growing between rows of vegetables or seeds that have not yet sprouted.

Biological control

Deliberately using living organisms (fungus, bacteria, etc.) to control weeds is unusual. However, there is a granular herbicide (Sarritor), developed from a pathogenic fungus (Sclerotinia minor), that can eradicate dandelions in your lawn. Apply the product when the daytime temperature is between 18 and 24°C, and water the lawn if the weather is dry. Most broad-leaf plants may be affected,so be careful using the product near beds of annuals and perennials. This fungus can also destroy clover.

Low-impact herbicides

These are less toxic than most synthetic herbicides. Such is the case of products based on acetic acid or fatty acids — non-selective contact herbicides that are particularly effective on annuals. Since perennials grow back quickly, several treatments are necessary to destroy them. Since they are non-selective, use a spot application method on the lawn.
There you have a range of options for controlling weeds in your garden. It is up to you to choose the most appropriate method(s), keeping in mind the fact that the lower the environmental impact, the better your garden will grow.

Read other advice >

Do you have questions about this blog?
Visit our Green Pages Or, go to the Horticultural information counter at the Botanical Garden for personalized service. One of our experts will be happy to give you more information.

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