Invasive Species Spotlight – Giant Hogweed

Name: Giant Hogweed (Heracleum mantegazzianum)

Origin: This species is native to the Caucasus Mountains of Eurasia. It was brought first to Europe and the UK in the 19th century, followed by the US in the early 20th century to be used as an ornamental plant in flower gardens.

NYS Presence: Giant hogweed has become established throughout the entire state.

Species Profile: Giant hogweed can grow to extreme heights of 15 to 20 feet! Its robust stems are covered with dark purple colored blotches and elevated nodules. Some of these stems can reach 4 inches in diameter! Giant hogweed leaves are proportional in size, with some reaching a width of 5 feet. These leaves are compound, greatly incised, and lobed. Its flowers grow in a flat-topped formation that can be easily compared to an umbrella. This cluster of flowers can reach up to 2 ½ feet across. A few species that can be mistaken as giant hogweed are as follows: native cow parsnip, native purple-stemmed angelica, and invasive wild parsnip.

Terry English, USDA APHIS Bugwood.org
Giant hogweed in flower, notice how it resembles Queen Anne’s lace. These flowers may be up to 2-1/2 feet in diameter compared to the 3″-4″ flower diameters on Queen Anne’s lace, photo by Terry English, USDA APHIS accessed from Bugwood.org.

Giant hogweed is often found in wetland areas near rivers, where it is known to out compete other species for habitat. When native plants are displaced, bank erosion may also increase. This plant is labeled as invasive or noxious due to its poisonous sap. This sap contains a chemical that sensitizes the skin to UV rays. If the skin comes in contact with the sap and is exposed to sunlight, the results may be blistering, severe burns, and/or painful sores. Irritation usually appears within 1 to 3 days after the exposure. This reaction is called “phytophotodermatitis”. Follow this link to the giant hogweed hotline number and other tips for what to do if you or someone you know encounters giant hogweed.

Resources:

Giant Hogweed

NYS DEC Giant Hogweed – Don’t Touch that Plant

Featured image: Antefixus21, accessed from Flicker

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