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Giant hogweed

Hogweed flowers

Giant hogweed

(Heracleum mantegazzianum)

Priority: -  Prevent

Tags: Terrestrial

Overview

Identification

Large upright plant up to 5 meters in height with hollow, ridged, green stems, some with reddish-purple spots

Leaves are dark green, toothed, and deeply cut into three large segments with stiff hairs on the undersides

Clustered white flowers in large umbrella-shaped heads up to 0.8 m in diameter

Reproduction

Biennial that reproduces by seed.

Habitat & Ecology

Prefers damp, rich soils. Found in riparian areas and along roadsides, ditches, and disturbed sites.

Impacts

Very large plant with large flowers. Poses a health and safety risk as it contains toxic sap that can cause burns, blisters, and scarring of the skin. Increases erosion of streambanks.

Management

Mechanical/Manual:

Use protective clothing and eyewear when handling this plant. Cut off flowers to prevent seed production. Excavate pants, severing roots 8-12 cm below the soil surface. Do not compost; ispose of all plant parts in strong garbage bags. Immature plants can be controlled by covering with black plastic or by mowing at 2 week intervals; 3-5 years of follow-up treatment may be required.

Chemical:

Foliar applications with glyphosate are most effective in Spring followed by a Summer application on late appearing sprouts.

Resources

Watch the Attack of the Giant Hogweed:

Download WorkSafe BC's Toxic Plant Warning on Giant Hogweed here

Download the Invasive Species Council of BC's Giant Hogweed TIPS brochure here