Supersized Plants! – Giant hogweed vs Cow Parsnip
Catherine is the Education and Outreach Coordinator for the Thompson Nicola Invasive Plant Management Committee (on Facebook @TNIPMC). This season, articles are dedicated to identifying native plants that are commonly mistaken for invasive plants. The series will provide tools and tips for telling the difference between invasive species and native look-alikes in our region. Look for more resources at www.tnrd.ca.
You’ve likely found yourself scratching your head, looking at an enormous plant wondering “is this the Giant Hogweed I’ve heard so much about”? Today’s article is focused on two plants that are often confused for one another: cow parsnip (native) and giant hogweed (exotic/invasive).
Both species have a large umbrella shaped ‘bouquet’ of small, white flowers. Both plants are large; however, giant hogweed is ‘supersized’, growing up to 4 m tall; cow parsnip taps out at a mere 2 m. The key defining difference between the two plant species is in their leaf shape. Giant hogweed has enormous leaves (up to 1.5 m across) that are deeply incised with pointy tips, while cow parsnip leaves are half the size and have more rounded leaf tips. The stem of giant hogweed also has purple spots on it, while cow parsnip stems may have purple coloring, but not defined blotches.
When examining these super-sized suspects, I caution you to do so from a distance or with proper personal protective equipment. Giant hogweed is a hazardous, federally listed noxious weed. Its sap contains phototoxic chemicals. If the sap encounters your skin and then is exposed to sunlight, it can cause severe skin irritation including painful, burning blisters and long-lasting scars. If the plant touches your skin, immediately wash the area with soap and water and protect from sunlight for 48 hours. Native cow parsnip is far less toxic, but it can still cause a rash or burn. Use caution around either plant.
Both species inhabit moist meadows, forest edges and riparian zones. Fortunately, giant hogweed is not yet known to occur in the TNRD. While it is possible for it to establish in the region, the super-sized plant you are likely to is our native cow parsnip.
Help keep our region free of invasive plants by being “Plant-Wise” and choosing non-invasive species for your property. If you suspect giant hogweed in our region, report it to the TNRD.
~ Catherine Tarasoff
Invasive Plant Outreach and Education Coordinator Thompson Nicola Invasive Plant Management Committee