Giant Hogweed

Giant Hogweed

Giant Hogweed

(Heracleum mantegazzianum)


The name is very fitting for these plants as they can grow to be several feet tall. Originally bought into America as an ornamental plant, they have spread throughout the region and prove to be a hazard to human populations. It is often found in roadside ditches, making it an issue for city workers or individuals who are responsible for maintaining these areas. The plant produces a sap which when comes into contact with skin and then sunlight can produce a severe allergic reaction. Some people even get severe burns and temporary blindness. This plant is very similar in look to queen Annes lace but hogweed is far larger. Hogweed can also have a distinct purple spotting on the stem, accompanied by small hairs.


Originally from Asia being brought over as an ornamental garden plant, this species has spread throughout the US and to many parts of Canada ranging from BC to Quebec. Here in Ontario, we see the plan in most of the southern region and as far north as Timmins.

Giant Hogweed stem

Impacts & Control

Due to the size of the plant, there is a possibility for shading the ground and blocking native species from growing. The main impact of hogweed is the threat of its photosensitive sap when the sap gets on humans’ skin and is exposed to the sun it will burn and bubble up potentially giving you severe burns. 

By far the threat to humans is the most severe impact of this species, with workers such as city greenskeepers being at high risk, this is due to their responsibility of keeping roadway ditches and other spaced mowed. 

Landowners who have giant hogweed on their properties are advised to attempt removal in early spring while wearing full protective gear. Recommended techniques are hand pulling with suitable equipment and placing the plant in a black garbage bag until it dries up, then you can dispose of it. 

It is not recommended to mow or weed wack these plants as it can spray the dangerous sap onto you.

If needed, the Ministry of natural resources does permit the use of roundup, only if directly applied to the hogweed and within certain restrictions.

Similar Species

Cow Parsnip
Queen Anne’s Lace
Wild Parsnip

Lookalikes- Giant Hogweed is very similar looking to species such as Cow Parsnip, Queen-Anne’s Lace and less similar Wild Parsnip. Due to multiple lookalikes being just as dangerous as Giant Hogweed it is safe to stay away from them in any case. A good distinguishing factor is the shape of the Hogweed leaf as it is very unique in shape and large. See some lookalikes to the right of the page.

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