Is there a Monster Lurking in Your Backyard?

Something strange and harmful may be hiding in your own back yard, silently waiting for you to make contact so it may poison you with its milky sap. It lures in your children with its fairytale appearance.  It causes burns that turn into blisters which turn into purple and black scars disfiguring your body. They cause your eyes to burn, blinding you for life. What could this terrible monster be? It’s the giant hogweed, a noxious plant invading the country working its way across one backyard at a time.

Photo Credit: City of Hamilton

The giant hog weed grows to 6 meters high (average height of human male 1.75 meters)  and produces large clusters of white flowers in umbrella shapes growing up to 75 cm across with a flat top.  Its identifying features are its size their prickly stalk, its purple spotted stem with purple streaks on stalks and its deeply cut leaves with coarse edges.

Photo credit: City of Hamilton

The plant produces a white watery sap found all over the plant. When contact with skin occurs and is exposed to sunlight, the chemicals bond with skin cells causing phytophotodermatitis (serious skin inflammation causing burning and blistering of the skin) (Chan et al, 2011). Even when the smallest amount of sap enters the eye can cause temporary or permanent blindness if not flushed out properly. If contact is made it can easily be stopped by flushing out the sap from eyes and scrubbing skin thoroughly with soap and water, if this does not work medical attention will be needed.

The weed was first brought into the country from Europe by gardeners hoping to grow the towering, majestic plants in their gardens unaware of the human hazards it can cause (Pyšek et al, 2008). The plant spread easily growing in many environments as long as sufficient sunlight is available yet preferring waste lands such as abandoned parking lots and roadsides. It is highly invasive and can occupy large spaces in short amounts of times. This is accredited to its highly successful reproductive strategy. One plant can send out tens of thousands of seeds that can survive on the ground for years. They can be spread easily by wind or water spanning far distances with ease.

This weed has been highly successful in Canada ranging from British Columbia across the country to Newfoundland. It has caused much media attention lately as the small populations in many provinces have exploded in size. Several provinces have released media warnings about the effects urging the public to report sightings. Giant Hogweed was discovered in the capital city of St John’s seven years ago but has only recently become a problem. Memorial Universities Botanical Gardens scientist Todd Boland has urged the province to take this problem more seriously by imposing an eradication program.

If you spot this noxious plant on your property you are urged to contact landscape professionals for identification and removal. The plant can be removed by land owners at their own risk during certain times of the year. Avoid touching the plant during summer as they are much too sappy and large at this stage they can be controlled by cutting off blooms before they have a chance to seed. During spring when they are smaller and easier to handle round up or common weed killer can be sprayed on the plant and removed with a spade after the plant has died. Although this should effectively eradicate the plant, seedlings may still regenerate.  

Photo Credit: Jason Marshall

Another interesting and controversial invasive plant is the Purple Loostrife which we will discuss next week.

Works Cited

Chan, J. C. Y., Sullivan, P. J., O'Sullivan, M. J., & Eadie, P. A. (2011). Full thickness burn caused by exposure to giant hogweed: Delayed presentation, histological features and surgical management. Journal of Plastic, Reconstructive and Aesthetic Surgery, 64(1), 128-130. Retrieved from SCOPUS database.

Nehrbass, N., & Winkler, E. (2007). Is the giant hogweed still a threat? an individual-based modelling approach for local invasion dynamics of heracleum mantegazzianum. Ecological Modelling, 201(3-4), 377-384. Retrieved from SCOPUS database.

Pyšek, P., Jarošík, V., Müllerová, J., Pergl, J., & Wild, J. (2008). Comparing the rate of invasion by heracleum mantegazzianum at continental, regional, and local scales. Diversity and Distributions, 14(2), 355-363. Retrieved from SCOPUS database.

Canada Press. "Researcher Warns of Hogweed Spreading Nationwide." CTV News. CTV News, 11 July 2010. Web. 05 Mar. 2012. <http://www.ctv.ca/CTVNews/SciTech/20100711/hogweed-100711/>.

CTV News Staff. "Think You've Spotted Giant Hogweed? Here's How to Tell." CTV News. CTV News, 15 July 2010. Web. 05 Mar. 2012. <http://www.ctv.ca/CTVNews/SciTech/20100715/hogweed-cullen-100715/>.

"Giant Hogweed Dangerous: People Warned to Stay Away from Giant Hogweed ~ Watch Pakistani Indian TV Channels| Webcam | Videos Online." Watch Pakistani Indian TV Channels| Webcam. Channels Pk. Web. 05 Mar. 2012. <http://www.channelspk.in/2011/07/giant-hogweed-dangerous-people-warned.html>.

Halfnight, Drew. "Giant Weed That Burns and Blinds Spreads Across Canada." National Post. National Post, 13 July 2010. Web. 05 Mar. 2012. <http://news.nationalpost.com/2010/07/13/giant-weed-that-burns-and-blinds-spreads-across-canada/>.

"Hogweed." Botanical Garden. Memorial University Botanical Garden, 27 July 2010. Web. 05 Mar. 2012. <http://www.mun.ca/botgarden/news.php?readitem=160>.

"Identifying Giant Hogweed." City of Hamilton. City of Hamilton, 2012. Web. 05 Mar. 2012. <http://www.hamilton.ca/CityDepartments/PublicWorks/Parks/Hogweed identification.htm>.

Marshall, Jason. "Everyone Going Hog Wild for Hogweed." YourOttawaRegion. Ottawa Region, 16 July 2010. Web. 05 Mar. 2012. <http://www.yourottawaregion.com/news/article/848827--everyone-going-hog-wild-for-hogweed>.