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Giant Hogweed

Giant hogweed
Photo Credit: Thomas Denholm, New Jersey Department of Agriculture, Retrieved from Bugwood.org (Image Number: 2121076), used under CC BY 3.0 US, modified from the original

Common Name: Giant Hogweed

Scientific Name: Heracleum mantegazzianum

Habitat: forests - open areas, forests - wet areas, ditches

Provincial Designation: Prohibited Noxious

Prohibited Noxious weeds are plant species that are designated as "prohibited noxious" in the Alberta weed regulation. Prohibited noxious weeds must be destroyed, meaning all growing parts need to be killed or the plant's reproductive mechanisms need to be rendered non-viable.

Origin

Giant hogweed is native to the Caucasus and was introduced to North America. It was used as an ornamental garden plant and its seeds were used in cooking.

Legislated Because

It can out-compete native plants in moist and wet areas and poses a human health concern. Giant hogweed's sap sensitizes skin to UV radiation and upon exposure can cause painful burns and blisters that may lead to hospitalization.

Description

The single white flowers have five petals and are 5-15 mm wide. They are arranged in compound umbels with rounded tops up to 1 m diameter. Each compound umbel has more than 50 umbel stalks.

The leaves are huge and can grow up to 3 m in diameter. The leaf is palmate or pinnate. The Leaflets that have lobed and/or serrated edges.

The thick stem is hollow with red blotches and stiff hairs. Giant hogweed is an impressive and uniquely large plant that grows up to 6 m tall.