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Sept. 27, 2022

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Beware of giant hogweed, Clark County warns

Sap of invasive weed causes burns, blisters

By , Columbian staff reporter
Published:
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Clark County is warning people to be wary of giant hogweed in the Salmon Creek watershed. Sap from the invasive weed can cause blisters and scarring if it comes into contact with human skin.
Clark County is warning people to be wary of giant hogweed in the Salmon Creek watershed. Sap from the invasive weed can cause blisters and scarring if it comes into contact with human skin. Clark County Public Works Photo Gallery

Clark County is warning residents to be wary of an invasive weed with sap that can cause severe burns and blisters.

Giant hogweed, also called giant cow parsley, can grow 15 to 20 feet tall and produce leaves up to 5 feet wide.

Magan Reed, spokeswoman for Clark County Public Works, said batches of the noxious weed have been found along Salmon Creek, from Northeast 72nd Avenue near Pleasant Valley to Northeast 182nd Avenue east of Battle Ground.

“Most of it is not on county right of way, so we are trying to reach out to property owners,” Reed said. “We really need property owners to look at their property and give us a call.”

Property owners who believe they have giant hogweed on their land are asked to email the location along with photos to weed.board@clark.wa.gov. Clark County Vegetation Management can be reached by calling 564-397-6140.

Giant hogweed has stems with distinctive purplish-red bumpy blotches and stiff bristles. It can be easily confused with cow parsnip. Giant hogweed is much bigger, and its purple blotches are more raised and bumpy than cow parsnip, which is native to this region.

According to the county’s website, giant hogweed’s clear, watery sap “contains a phototoxin that causes human skin to be hypersensitive to sunlight, resulting in burns and blisters. Scars can last a year or more, and direct contact with eyes can result in temporary or permanent blindness.”

Giant hogweed is listed as a Class A noxious weed in Washington, which means property owners are required to eradicate it. The Washington State Noxious Weed Control Board advises wearing protective clothing and avoiding contact with the plant’s toxic sap.

The state’s website has a map indicating giant hogweed was most prevalent in Pierce and Kitsap counties in 2018. Fewer than 10 acres in Clark County were infested with the weed, which is native to the Caucasus Mountains and Southwest Asia.

Reed said the plant’s seeds fall off easily and can be dispersed through water, which is why giant hogweed has been found along Salmon Creek.

Columbian staff reporter

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