The toxic sap of giant hogweed, seen growing wild in Oregon and Washington state, can cause skin sensitivity, burns, blisters and scars, warns Clark County Public Works, which discovered some of the dangerous plants in Washington state’s Salmon Creek area.

The federally regulated noxious weed, with an umbrella-shaped flower head, exudes a clear watery sap that sensitizes skin to the sun. People who have been exposed to it have developed severe burns leading to blistering and dermatitis. Those blisters can turn into purple or black scars.

Anyone who thinks they’ve found live or dead giant hogweed should avoid touching it and email a picture to Clark County Public Works at weed.board@clark.wa.gov or contact the Oregon Department of Agriculture Noxious Weed Control Program at 503-986-4621 or 866-INVADER, depending on the location.

Do not touch this toxic plant! Giant Hogweed has been spotted in Clark County, in Salmon Creek area. Clark County Vegetation Management is working hard to eradicate it. If think you have found it, please email us pictures and provide the location: weed.board@clark.wa.gov pic.twitter.com/jmoHGrU3EQ — Clark County WA_PW (@ClarkCoWa_PW) July 11, 2019

People who must handle giant hogweed prevent skin contact by wearing protective gloves, long sleeves, pants, a hat and eyewear, according to the Oregon Department of Agriculture.

If you accidentally come in contact with the plant’s sap, wash immediately with soap and cold water (hot water promotes absorption), avoid direct sunlight and consult a healthcare provider.

Children are attracted to the hollow, dark reddish-purple spotted stems, which have a blister-like texture and a bristle emerging from each bump.

White flower clusters bloom from mid-May through July and can easily be confused with native cow parsnip.

The weed spreads by its papery, disc-like seeds that float down streams and land on banks. A majority of the sites in Oregon were planted by gardeners who were unaware of its invasive and toxic qualities, according to the state’s department of agriculture.

Giant hogweed, which can reach 10 to 15 feet tall, is native to the Caucasus Mountains in western Asia.

Terry English/USDA APHIS PPQ/Bugwood.org

Early in the 20th century, hogweed was planted in arboretums as a curiosity due to its massive size. It escaped the confines of managed gardens and quickly adapted to the surrounding areas, spreading throughout parts of Europe and North America, including parts of Maine, Maryland, New York, Washington and, more recently, the northwestern corner of Oregon.

--Janet Eastman | 503-294-4072

Kale Williams contributed to this story.

jeastman@oregonian.com | @janeteastman

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