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Luckily, school is not in session.
Giant Hogweed (Heracleum mantegazzianum) was found last week at Hartley Elementary School in Gresham. This plant is very invasive and very dangerous. The sap of Giant Hogweed makes human skin extremely sensitive to sunlight, so much so that a burn lesion will appear within 15 hours of exposure. The lesions will often develop into scars. Because this plant is a public health hazard and invasive, Giant Hogweed is listed by the Oregon Department of Agriculture as a noxious weed. If you would like to see an example of the lesion do a web search for 'giant hogweed burns', but be warned that the photos are gruesome.
We are extremely fortunate that a Reynolds School District employee noticed this plant, had seen Hogweed before, and reported it to the City of Gresham. EMSWCD staff visited the site and confirmed that it is indeed Giant Hogweed. This infestation probably went unnoticed because Giant Hogweed plants do not flower for up to four years. It also dies back in the fall.
These pictures give you an idea of why it is called 'giant' and the proximity to the school's playground.
Staff from the Oregon Department of Agriculture will apply herbicides to the infestation this week. EMSWCD staff will monitor the site to watch for re-growth this summer and again next spring.
We strongly encourage you to watch out for this plant and to report any plant that you suspect could be Giant Hogweed to us. It does look like our native Cow Parsnip, but Giant Hogweed is much larger. Hogweed plants can reach 15 feet tall with 3 to 5 foot wide leaves and 1-2.5 foot wide flowers. Cow parsnip rarely grows above 6 feet and its leaves and flowers are half as big. Giant Hogweed stalks are 2 to 4 inches wide, hollow, bumpy, and they have deep red to purple blotches.
This Oregon Department of Agriculture web page can help with identification: http://www.oregon.gov/ODA/PLANT/WEEDS/weed_gianthogweed_id.shtml
REPORT SIGHTINGS! Please report suspected plants to Online Invasive Species Hotline at www.oregoninvasiveshotline.org or call us, 503-222-SOIL.
Avoid contact with the live or dead plant. If your skin does come in contact with any part of a Giant Hogweed plant, immediately wash the area with soap and cold water, stay out of the sun, and contact your doctor.
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