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Undesirable plants

Japanese knotweed (Polygonum cuspidatum, syn. Fallopia japonica)
Photo: CC BY-SA 2.0 Wikimedia Commons (Kenneth Allen)
Polygonum cuspidatum, syn. Fallopia japonica
  • Polygonum cuspidatum, syn. Fallopia japonica
  • Taraxacum officinale
  • Common plantain (Plantago major)

A weed by any other name…

Weeds are plants that grow where they are not wanted. With the exception of certain plants such as poison ivy, ragweed and invasive exotic plants like Japanese knotweed and giant hogweed, these plants are not “bad” in themselves.

A number of weeds are actually edible (dandelions, strawberries, clovers, common purslane, etc.) and/or medicinal (ground-ivy, dandelions, plantain, coltsfoot, etc.).

Weeds grow on sites where conditions are suitable to their development. In fact, many of these plants provide useful information about the site. For instance, dandelions grow well in compacted, calcium-deprived soil. Wild strawberries prefer acidic, sandy sites. And plantain often thrives in lawns mowed too short and where the soil needs to be aerated.

Think prevention first

The best way to keep weeds out is to ensure that your lawn and other plants benefit from the right growing conditions and proper care.

Thus, to obtain a healthy lawn with grass that can compete effectively with weeds, just follow these golden rules:

  • Mow the lawn to 7.5 cm (3 inches) in the summer, and leave the grass clippings where they fall, watering deeply as needed
  • Aerate compacted soil
  • Feed the lawn with compost
  • Apply lime if necessary
  • Fertilize in moderation with 100% natural products
  • Reseed bare patches.

In new borders, organic mulch (chopped dead leaves, ramial chipped wood, buckwheat hulls, etc.) effectively prevent weeds and keep the soil moist.

Mulch is not necessary in landscapes where plants’ foliage completely covers the ground, as the shadow cast by the organic canopy will prevent the germination of most weed seeds. In this case, auto-composting by letting dead leaves, twigs and wilted flowers decompose into the soil is relevant. They will form a feeder layer for the soil’s plants and micro-organisms.

If your site isn’t suited to growing a lawn or certain other plants, choose plants that are better adapted to your conditions (ground covers, shade plants, etc.) or use inert materials (paver, gravel, etc.) in some parts of your garden.

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