Plants to keep an eye on!


JULY 6, 2022



Are you a fan of hiking, the great outdoors and quiet nature walks?


The physical and mental benefits of walking in nature have been scientifically proven. This disconnection from the hustle and bustle of city life and daily stress is excellent for calming the mind and reducing anxiety. Taking regular walks in the fresh air also boosts the immune system, lowers blood pressure and boosts cognitive capacity.


Some plants, however, can quickly spoil your experience. Among the varieties most likely to come your way are giant hogweed, wild parsnip and poison ivy. All it takes is a brief contact with your skin to cause very undesirable effects.


Familiarizing yourself with these plants and paying attention to the environment around you will help you spend pleasant and beneficial moments in nature.



This noxious plant can be found throughout the province in cool, damp soil conditions, such as in ditches, in fields and on the banks of streams.


Measuring between 2 and 5 m in height, Giant Hogweed certainly doesn't go unnoticed.

  • Its broad, sturdy stem features dark-red spots and coarse white hairs.
  • Its serrated-edged foliage is up to 1.5 m wide by 3 m long.
  • Its white, umbrella-shaped flowers can be 25 to 50 cm in diameter.


Why is this plant considered toxic?

The sap of this plant contains phototoxic toxins. In other words, within 48 hours of skin contact with the sap combined with exposure to light, sometimes severe lesions will appear.

  • Redness and swelling of the skin
  • Blisters
  • Minor or, more rarely, severe burns (1st or 2nd degree)


In case of skin contact :

  • Remove sap quickly with absorbent paper, without rubbing.
  • Rinse the area well and wash with soap.
  • Wash clothes immediately.
  • Avoid exposing the area to light and protect it for at least 48 hours, or 1 week in the case of burns.
  • Apply sun protection SPF 30 minimum, for 6 months to protect against UV rays.


In case of contact with eyes :

  • Rinse thoroughly for at least 10 min.
  • Avoid exposure to light, using sunglasses with dark lenses.️
  • Seek prompt medical attention.



This toxic invasive species is in the same family as Giant Hogweed. Wild parsnip is found along the edges of fields, roads and railroads, as well as in fields and ditches.


Smaller than hogweed, this plant grows to between 0.5 and 1.5 m tall.

  • Its thick stem is green and smooth. Like hogweed, it has hairs, but fewer of them.
  • Its serrated leaves are composed of 2 to 5 pairs of leaflets (small leaves) “growing opposite each other on the stem, with a diamond-shaped leaflet at the tip” (Government of Ontario, 2015).
  • Its umbrella-shaped, yellowish-green flowers are 10 to 20 cm in diameter.


Does wild parsnip cause the same symptoms as hogweed?

The sap of this plant also contains phototoxic toxins that can cause severe dermatitis. However, these lesions are generally benign compared to those caused by hogweed.


In case of skin contact :

  • Wash the affected area with soap, then rinse thoroughly with clean water.
  • Wash hands.
  • Wash clothing if it has been in contact with the plant.
  • Avoid exposing the area to light and protect it for at least 48 hours, or 1 week in the case of burns.


To remove :

  • Put on the necessary protective gear (goggles, long clothing, gloves, rubber boots).
  • Pull up the plant, removing as much of the taproot as possible with a round shovel, spade or long-handled knife.
  • Cover the infested area with geotextile fabric after cutting roots and stems to prevent regrowth, or follow up regularly to remove any regrowth.
  • Wash your clothes and tools.


Please note:

  • For large infestations, professional extermination is preferable.
  • The best time to remove this plant is in spring, when the soil is moist.
  • Do not burn or compost wild parsnip plants.



This plant adapts to a variety of environments. It can therefore be found just about anywhere, such as along the edges of paths and nature trails, woods and watercourses, and on vacant lots.


Poison ivy is a bushy or sometimes climbing plant, ranging in height from 20cm to 1m.

  • Each leaf consists of 3 pointed leaflets.
  • Its glossy foliage changes color with the seasons. It's reddish in spring, green in summer, then various shades of yellow, orange and red in autumn.
  • During flowering, in June and July, clusters of small cream or yellow flowers appear beneath the plant's leaves.


Why avoid this plant?

Poison ivy is a poisonous plant whose sap, composed of a toxin called Urushiol, can provoke a strong allergic skin reaction. The reaction can occur following direct contact with the plant or an object soiled by the sap, or following inhalation of the toxic fumes produced by the plant's combustion*.

  • Symptoms appear within 24 to 48 hours of contact.
  • Strong itching
  • Sensation of pain or burning
  • Redness and swelling of the skin
  • Blistering


*Note that burning poison ivy “can cause extremely painful inflammation of the lungs and serious respiratory problems that can lead to death” (Gouvernement du Québec, 2021c).


In case of skin contact:

  • Wash affected area with cold water and mild soap as soon as possible.
  • Wash all clothing that has been in contact with the plant (including shoes, socks and laces).
  • Be careful to remove any pieces of the plant that may have become embedded under your fingernails.
  • Avoid rubbing too hard.


*Seek immediate medical attention if you have inhaled smoke from burnt poison ivy plants or accidentally ingested sap.


To relieve symptoms

  • Apply compresses of cold water and baking soda.
  • Take warm baths with colloidal oatmeal powder.
  • Consult a pharmacist for the best treatment for your needs.


* Consult a doctor if symptoms are severe, widespread or located in a sensitive area (face, eyes, genital region, etc.) and if there are signs of infection (increased pain, pus, fever, etc.).


How can I tell the difference between poison ivy and ragweed?


These 2 plants are often confused. However, they can be differentiated by their appearance and their effects on health.


Visual differences

While poison ivy has glossy foliage, with each leaf made up of 3 pointed leaflets, ragweed has more of a serrated, carrot-like foliage.


Health effects

As mentioned above, poison ivy causes a severe skin reaction on contact with its sap. Ragweed, on the other hand, is harmless to the touch, but produces airborne pollen that can cause an allergic reaction. It is one of the main causes of seasonal allergic rhinitis, also known as hay fever.



  • Government of Ontario. July 23, 2015. “Wild parsnip fact sheet”.
  • Government of Quebec. 2021a. “Giant Hogweed Burns”.
  • Government of Quebec. 2021b. “Recognizing and eliminating Giant Hogweed.
  • Government of Quebec. 2021c. “Allergic reactions caused by poison ivy.
  • Government of Quebec. 2021d. “Recognizing and eliminating poison ivy”.
  • Morita, E., Fukuda, S., Nagano, J., Hamajima, N., Yamamoto, H., Iwai, Y., Nakashima, T., Ohira, H., & Shirakawa, T. 2007. “Psychological effects of forest environments on healthy adults: Shinrin-yoku (forest-air bathing, walking) as a possible method of stress reduction”. Public health, 121(1), 54-63.
  • Tsunetsugu, Y., Park, B. J., & Miyazaki, Y. 2010. “Trends in research related to ‘Shinrin-yoku' (taking in the forest atmosphere or forest bathing) in Japan”. Environmental health and preventive medicine, 15(1), 27-37.
  • Quebec City. 2021. “Wild parsnip.


Émilie Bédard

Communications Manager