Last updated April 3, 2023

Many Montrealers are allergic to ragweed. When this invasive plant blooms in August, its pollen is the cause of hay fever.

Ragweed is everywhere in our environment. Residents are encouraged to destroy it because of its harmful effects. Learn more about this weed.

Ragweed characteristics

  • In August, ragweed flowers look like yellowish spikes.
  • Its thin, deeply indented leaves are uniformly green on both sides.
  • Mature plants are between 10 and 100 cm high.
  • Ragweed starts to release pollen in August, with maximum concentrations and high risk of allergic reactions between August 25 and 30.
  • Ragweed is found on the edge of sidewalks, alleys, gravel piles, railways, construction sites, vacant lots, etc.

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