What You Can Do About It

Prevention and Control

The best time to stop the spread of purple loosestrife is late June, July and into early August. During this time plants are flowering and easily recognizable and have yet to go to seed. Removing the plant once the seeds have developed may cause further spread as the seeds fall off the plant during removal.

When removing purple loosestrife from a garden, it is important to make sure the entire root mass, and all the pieces, are removed. Roots can reach 30 cm (1 foot) or deeper into the soil.  Since purple loosestrife can re-establish from just pieces of the plants, care should be taken when digging it out.  Once removed, place the plant in a black garbage bag and let it dry completely.  Placing the bag in a hot, sunny location will speed up this process.

Once the plant is dried out it may be burned, where permitted, or placed for disposal in the landfill. Make sure to burn the plants completely, or double bag them to avoid contaminating landfill sites. The removal area should be monitored the next growing season and beyond because there will a seed bank remaining in the soil.  There are many alternative garden perennials that can be planted in place of the purple loosestrife.

Removing purple loosestrife from wetland areas is not easy. Herbicides cannot be used in many of the areas where purple loosestrife is found.  In areas with large infestations, digging up the plant is labour intensive, can disturb the soil, and increases the chance of spreading seeds.  In Manitoba, biological control has been used to help control the spread of purple loosestrife.

 

Canada and the United States are using specialized leaf eating beetles from Europe to control the plant. These beetles are safer than using chemicals and only eat the purple loosestrife plants. This form of biological control has successfully managed large areas infested with purple loosestrife.

 

Infestation in Netley-Libau Marsh, Manitoba, 1999 (Below)

Purple Loosestrife Infestation

Manitoba Conservation Ducks Unlimited City of Winnipeg Invasive Species Council of Manitoba