Toxic weed discovered in Ottawa

Giant Hogweed fact sheet

Background

Giant Hogweed is a serious invasive plant that poses a moderate threat to human health and safety. The plant is native to Europe and Asia and was introduced to Canada as an ornamental. It is found in many areas in southern Ontario, and has recently been discovered in Renfrew County and small populations have been confirmed in theOttawa. In each case municipal staff has started localized removal of the plant.

Description

Giant Hogweed is a long-lived perennial plant. It can take three to fouryears before flowering and flowers only once in its life. It can range in height fromone to 5.5 metres. Plants produce huge leaves that are up toa metre in width. Leaves are deeply cut, with large lobes and sharp teeth on all leaf margins.

It has sharp pointed bumps on stems and leaf petioles. Stems have reddish purple flecks and are often entirely purple at the base. Stems are mostly hollow and up to 10 cm in diameter. Stems and petioles are densely hairy.

Giant Hogweed flowers from June to August with white (sometimes pinkish) flowers in large clusters.

Distribution and habitat

Primarily found along roadsides, stream banks and disturbed open areas. Plants reproduce well on disturbed sites, and prefer full sun and open habitat common along roadsides and ditches in rural areas.

Ecological impact

Giant Hogweed can shade out and outcompete native vegetation, which is a concern in riparian areas along stream banks and natural areas.

Human health concerns

This plant is poisonous. Its hollow stem, leaves and plant hairs produce a sap if broken thatcan cause serious skin inflammation on contact. If contaminated skin is exposed to sunlight a more serious reaction can occur including blisters, discolouration and scars. Contact with eyes can lead to temporaryloss of vision or blindness.

Giant Hogweed contact with bare skin should be avoided this includes all portions of the plant. If contact with skin occurs, avoid exposure to sunlight and wash the site immediately. If a skin reaction occurs, seek medical attention.

Those working to control this plant should use goggles and waterproof gloves. Long sleeves, pants and boots should be worn; synthetic materials work best since most fabrics will absorb plant sap or can be penetrated by the plant.

Clothing that comes in contact with plants should be washed. Equipment used to control the plant should be washed with water immediately.

Management and control

Giant hogweed is mainly spread by soil movement and contaminated equipment but can still be found in private gardens. Minimizing soil movement and regular equipment washing can help prevent new introductions.

This plant takes several years to reach its full size and to reproduce.It is easy to see and identify due to its habitat and large size. It shouldnot be removed with a brush saw or weed-eater, but can be destroyed with over-the-counter herbicides.

Suspected findings of Giant Hogweed should be confirmed through the City of Ottawa at 311, or throughthe Natural Resource Information Centre at 1-800-667-1940, or by visiting www.ontarioweeds.com