Purple loosestrife (Lythrum salicaria) is a woody half-shrub, wetland perennial, considered regionally noxious under the BC Weed Control Act. Purple loosestrife is found in wet areas at low- to mid-elevations, growing in ditches, irrigation canals, marshes, stream and lake shorelines and shallow ponds. It is common in the Lower Fraser Valley and frequent on southern Vancouver Island and in the Okanagan. There are also localized patches in the Kootenay and Omineca regions.

Shrub-like in appearance, purple loosestrife has stiff, four-sided stems ending in dense spikes of showy purple flowers. Plants have narrow, stalkless leaves, growing up to 3 metres in height at maturity.

Often confused with fireweed, purple loosestrife is an escaped ornamental that tolerates a wide range of weather conditions and will grow in standing water. Seeds distribute through water, humans and animals, with a single plant producing over 2.5 million seeds that drop in early fall when temperatures cool. Dense stands of purple loosestrife threaten plant and animal diversity in wetland ecosystems.

Refer to Weeds BC for information on prevention and control methods.