Monday, May 30, 2011

Profile on Invasives: Giant Hogweed

Giant Hogweed

Heracleum mantegazzianum

This post marks the beginning of the "Profile on Invasives" series of the blog.

I will post in detail about some of the invasive species most commonly found in Muskoka.

Do you have a suggestion for a species you'd like to see covered?

Let me know by leaving a comment below!

What is it?
Giant Hogweed is a biennial or perennial plant, flowering only once in its lifetime and reproducing only by seed. Plants forming rosettes to 1m high the first year; in the second year, either sending up a flowering stem, or remaining vegetative and producing a very large rosette of huge leaves, these including their petioles, up to 2m high, and flowering in the third year. As it goes through these stages, its' appearance changes (see photos below).

Giant Hogweed grows for 3-5 years and 4-5 metres tall before flowering. Flowering occurs from June to August, at which point the seeds are released. Once the seeds are released the plant dies. Seeds are dispersed by wind, water and humans, and can survive in the soil for 7 years. Each plant can release between 20,000 to 100,000 seeds, resulting in high rates of spread.

Where does it grow?
Giant Hogweed grows in moist environments, generally near streams, lakes and ponds.
Why is it dangerous?
Giant Hogweed competes with native species for light, and can change the composition and reduce the diversity of native plant communities.

Giant hogweed contains a clear, watery, toxic sap. When this comes into contact with human skin it reacts with sunlight which results in severe burns on the skin within 15 minutes of exposure. The burns are extremely painful as evidenced in the photos below.

The sap is also carcinogenic and teratogenic, meaning it can cause cancer and birth defects. If the sap gets in your eye, the chemical in it can singe the cornea and cause temporary or permanent blindness.
What is the District of Muskoka doing about it?
On May 26th, Moose FM reported that the "Township of Muskoka Lakes is doing what it can to protect residents from the dangers of Hogweed. At a special council meeting last week, council directed staff to take action to eliminate Giant Hogweed from public land. This includes the use of pesticides and warning signage in known areas. The resolution will now go to District Council, where councillor Brad Burgess will ask to speak to members about undertaking a similar resolution district wide." Stay tuned...
What should you do if you find giant hogweed?

  • DO NOT touch the plant!

  • DO NOT try and control the plant yourself; contact a pest control expert or your town/municipality

  • Report your sighting to the Invading Species Awareness Program

  • Keep children and pets away from the plant

  • Help stop the spread of invasive plants of all kinds by removing seeds, fluff, plant material from your clothing, shoes, pets, and bikes before leaving a natural area.

  • Should you touch Giant Hogweed, wash the affected area immediately with soap and cool water. Avoid sunlight and seek medical attention.

Similar Plants

Giant Hogweed has a similar appearance to a few other common plants in Muskoka:

More Information and Photos

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