Purple loosestrife is a wetland species native to Europe brought to North America in the early 19th century. The highly invasive plant was most likely introduced by European ships. They used soil as a ballast in their ships and discarded it once they reached their destination. Thus depositing the seeds that were carried in the soil and transplanting them across continents. The plant was also spread by early settlers using it for ornamental purposes in gardens.
Since it was brought to North America, purple loosestrife has become a serious problem in wetlands. The plant forms dense patches with thick masses of roots that can extend over large areas. The patches reduce nutrients, space, biodiversity, and habitat for native plants and wildlife. A single plant can grow as many as 30 flowering stems (“Purple Loosestrife.” Ontario's Invading Species Awareness Program). These stems in turn can produce up to 2 million seeds a year. The seeds are then easily spread by wind, water, wildlife, and humans.
It can be easily identified by its tall stocks topped with large pink/purple flower spikes. Can grow up to 2 m tall and form 1.5 m crowns. It has a woody square shaped stem. The leaves are simple and lance shaped with smooth edges and fine hairs (“Purple Loosestrife .” Invasive Species Centre).
The best form of control for this invasive is to prevent the spread as well as preventing new plantings. Pulling the plants can be effective in small patches or with a large group of people for larger patches as it is a deeply rooted plant that is hard to remove.
The Moose Jaw River Watershed Stewards recently organized a volunteer day on August 4th sponsored by Gibson Energy. The goal was to tackle a large patch of Purple Loosestrife along the Moose Jaw River. This was part of a proposed 3 year project to remove the patch that dominates a large portion of the bank. The project started in 2020 with a pull focused on the north side and continued this year with the pull focused on the south side. We're hoping to tackle the central portion next year. We have been successful so far in the purple loosestrife not coming back where it has been pulled. Once we have the whole patch pulled we will move to monitoring it in the coming years and doing small pulls where necessary.
If you find purple loosestrife while out enjoying the river please let us know. Check out our photo gallery below to see the MJRWS team and our awesome volunteers tackling this massive purple loosestrife patch.