Purple loosestrife invades the wetlands and gradually take them over. The weed ultimately chokes out all native vegetation, creating a dense purple landscape almost totally devoid of wildlife. Purple loosestrife came from Europe over a century ago. Its unrelenting spread across North America was aided by the absence of native predators.

In Canada, there are no herbicides registered for use against purple loosestrife in or growing close to water. Biological controls have only recently bee approved and it may be some time before there are adequate supplies of these insects for widespread use. Large scale wetland infestations are best left until environmentally safe control methods are readily available. Location and size of all sites should be documented NOW so they can be dealt with swiftly once control methods are in place.

Many concerned individuals and groups want immediate action. They want to so whatever they can TODAY to stop the spread of loosestrife into more wetland areas. Their actions are being focused on small strands of the weed in parks, natural settings and at home.


The entire plant must be removed to minimize the chance for regrowth. Dig out the root mass, making sure that you have removed ALL the pieces. The roots extend 30 cm (1 foot) or deeper into the soil. Grass or alternative flora may be planted or the area can be allowed to return to native vegetation.

Place ALL plant matter in a carton or a protected site so it can dry completely without the danger of being spread by wind, water, human or animal activity.

Once totally dried, the plant matter can be burned, packaged for disposal, or composted. When burning, make sure all plant matter is destroyed. When packaging, wrap securely in a plastic bag or container to avoid contamination at land fill sites. When composting, make sure that all plant matter is totally dried first so that living material isn't spread to other gardening or landscaping sites.

Purple loosestrife will re-root from the tiniest piece of root, stalk, leaf, flower, seedhead or even bits dropped from the wheelbarrow. Also, dormant seeds may germinate because of soil disturbance during removal activity! For these reasons, it's important to work carefully and keep site disturbance to an absolute minimum.

All the work should be completed by mid-summer BEFORE the flowers begin to so to seed. Seed formation starts at the bottom of the flower and progresses to the tip. Before taking action, check to see that no ripe seeds are present. If there are and there is a chance of spreading the seed, put the project on hold until next year.

Monitor the site for several years. New shoots may come up from root remnants. This new growth should be dealt with quickly.


A single plant is capable of producing 2.7 million seeds per year. Each seed can lay dormant for ten years or longer before germinating. Where plant digging isn't feasible, flower head removal helps retard the spread of the seed. Simple cut the head mid-summer BEFORE the flower sets seed. Remove and destroy flowering heads as outline in REMOVAL.


In plain and simple terms, purple loosestrife is one tough plant. It is a deep-rooted perennial that spreads like wildfire. No magical solution is immediately available, but some practical ones are on the horizon. A variety of techniques and tools will be needed to bring this exotic pant under control. Bio-controls and herbicides are two options which hold real promise. But the bottom line is that any control method must be environmentally acceptable.

A number of herbicides have proven effective in dry land control of loosestrife, but are still un-registered for that use. Registration procedures for these applications are underway. Initial research on herbicides now being tested in aquatic situations suggest an effective control is possible there too. However, this research is in the formative stage and it will be some time before an aquatic herbicide is registered.

While herbicides are used to "eradicate" weeds, biological agents are used to "control" them. They reduce weed densities to the degree that their impact on other species is minimized. Biological control is the most efficient and economical long term means of dealing with large infestations. Work is progressing with a number of European insects which have historically kept this plant under control on that continent. Three of these insects were recently approved for release in Canada.

Quick and effective use of biological and chemical control measures will only be possible in those areas where there is good documentation of infested sites. That's why it's important that every site be documented with a Purple Loosestrife Report Form sent to the Canadian Wildlife Federation. Sites can also be reported by calling 1-800-565-6305.

Purple Loosestrife FEATURES

Height: 3 to 6 feet (1-2 meters)

Stalk: square, woody, several stalks per plant

Leaves: smooth edges, opposite sides of the stalk, attached directly to the stalk

Flowers: long pink/purple spike, June to Sept.


For years, it was felt that commercially available hybrid cultivars (Morden Pink, Morden Rose, Morden Gleam and Dropmore Purple) were sterile and thus unable to produce viable seed. However, recent research shows that some of these domestic varieties can, in fact, cross-pollinate with wild strains and thus cause further spread. If you have purple loosestrife on your property and wish to replace it with an alternate plant, follow the steps outlined in this brochure.

The Canadian Nursery Trades Association and local outlets have bee quick to respond to the purple loosestrife challenge. Landscapers and home gardeners are now offered a wide variety of alternate perennial plants which pose no threat to the environment. The following is just a small sampling of what's available. See your local nursery or garden center for details on purple loosestrife replacements.

Spiked Speedwell

This mid-summer flowering perennial has blue, spike-shaped blossoms and grows to a height of a foot and a half. It does well in full sun, but also tolerates partial shade.


There are a wide variety of lilies with a vast range of colors. Different varieties flower from early summer to late fall and may grow as tall as six feet.

Siberian Iris

This perennial stands two feet tall and flowers through late spring and early summer with white, blue and purple blossoms. It requires a sunny to partially shady site.

Spiked Gayfeather

This five foot tall native of eastern Canada had pink, purple, and white blossoms from mid-summer to early fall. It requires full sunlight to partial shade.


Garden Sage

This summer blossoming plant features flowers which are violet to blue. It is drought tolerant, likes full sunlight and grows from a foot and a half up to three feet tall.

Brochure produced by Ducks Unlimited Canada with the support of Environment Canada/Canadian Wildlife Service and the Canadian Wildlife Federation. Distribution assistance from provincial and federal wildlife agencies, agricultural agencies, and private wildlife and naturalist groups. Special thanks to the Canadian Nursery Trades Association for their cooperation.

Canadian Wildlife Federation
2740 Queensview Drive
Ottawa, Ontario
K2B 1A2

Phone: 1-800-565-6305
FAX: (613) 721-2902