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Flowering Rush Removal

Flowering rush (Butomus umbellatus) is an exotic, invasive plant that was sold for use in water gardening up until the summer of 2010, but is now prohibited by law in Saskatchewan. Its invasive characteristics are similar to the better-known purple loosestrife in that it invades wetland edges and slowly displaces native species, forming a monoculture and ultimately killing the wetland. 

In 2002, a single population was found in a wetland in Saskatchewan but remained largely unknown until 2008. This is the first and only known escaped population of flowering rush that has established in Saskatchewan. Recognizing the danger of letting it spread to other nearby wetlands, the NPSS launched a project to map and eradicate the flowering rush in this wetland. In 2008 and 2009, the wetland was mapped to determine the extent of the spread of flowering rush. At the same time, vegetation and other data were collected, and the flowering heads of the flowering rush were clipped, bagged and burned to prevent seed dispersing. However, since flowering rush also spreads by rhizomes (creeping roots), the plants themselves had to be removed. In 2010, manual removal of the flowering rush plants began. Thanks to good volunteer turnout, approximately half of the flowering rush population was removed and the rest of the population had the flowering heads clipped to prevent seed spread. We also developed a protocol for manual removal of flowering rush, the first of its kind.

In 2011, most of the remaining flowering rush was removed by October. We also monitored the areas where flowering rush was previously removed to ensure that it didn't re-emerge. We found the previous year's removal efforts very effective as roughly only 25% re-emerged. These were promptly removed. This rate of success is very good and proves that the manual removal protocol that we developed is effective. In fact, Alberta is now using our protocol for some of its own flowering rush removal. By the end of 2011, only 5% of the original flowering rush population remained, which will be removed in 2012. The wetland was re-mapped and other nearby wetlands were searched in order ensure that flowering rush had not spread.

In 2012, manual removal started in August and continued until the remaining 5% of the original plants and any that reemerged from the previous year were removed. The site was also a tour stop for the Pacific Northwest Economic Region (PNWER) Invasive Species Committee as a model of an effective early detection and rapid response project. PNWER is an international organization (of which Saskatchewan is a member) and had their annual meeting in Saskatoon in 2012.

For 2013, the site was resurveyed to determine how many plants had reemerged, and also to re-map the wetland. Where flowering rush had received more than one year of removal, it was quite sparse and was easily removed again. Where the flowering rush had only been removed in 2012 for the first time, the patches were denser, the plants more vigorous, and it was as difficult to remove as the first time. 2013 is the first year that the flowering rush has put up a good fight. While the back of the wetland (which is the newest and least infested) is showing real progress, including complete eradication of whole areas, the front of the wetland along the road (the oldest and most entrenched flowering rush populations) is showing the least progress, though progress is still being made. By the end of 2013, all of the flowering rush will once again be removed and the site will be monitored in future years and any reemerging plants will be removed.

In 2014, the site was once again surveyed and re-mapped. The water levels were alarmingly high and caused a significant amount of complications to our project, such as site access, difficulty in removing plants in deep water (some were 1 m deep), reduced effectiveness of removal due to the depth of water, and increased potential potential for spread to the wetland on the other side of the road, as the water over-topped the road for part of the spring. Having water in previously dry areas also reactivated format flowering rush plants that had grown there a number of years ago when water levels were higher but had since gone dormant under unsuitable growing conditions. This was not something we had expected to happen, or even knew could happen. However, it was somewhat of a blessing in disguise as it showed us where all of the plants were so that we could remove them. By the end of the season, all flowering rush had been removed, representing approximately 5 tons of material!

2015 and 2016 were very successful despite the still higher than normal water levels. An average of 3 tons of material was removed per year, and the same data collection protocol was observed. In 2015 we also collected samples for genetic testing which was part of a North American wide study on Flowering Rush. The results of our samples showed that they are related to other populations in North America, although a source population in Europe has not yet been identified. The coalition working on this study is also involved in finding suitable insect biocontrol options for Flowering Rush with the hope of a widespread suppression effort.

2017 saw drastic declines in flowering rush numbers, with only 45 plants found. All were removed. This was the first year in which it was apparent that significant gains were being made and that collpase of the flowering rush population was imminent.

2018's efforts revealed only 8 flowering rush plants remaining in the entire wetland. Field work on the site required only one day to complete; this is down from weeks worth of field work to require the same objectives during the initial stages of the project when flowering rush was at its peak. The 8 flowering rush plants were removed and it is anticipated that none will be fouind in 2019, after which the site will enter the long-term monitoring phase.

If eradication of flowering rush is successful in this wetland, it will be one of the first successful early detection, rapid response and eradication efforts against a new invasive species in Saskatchewan (and one of the first in Canada as well). 

Thank-you to the following organizations for their generous financial contribution to this project in past years: Environment Canada (Invasive Alien Species Partnership Program and the Environmental Damages Fund) and the Saskatchewan Ministry of Environment (Fish and Wildlife Development Fund).

Funding for this project in 2013 has been provided by Agriculture and Agri-Food Canada through the Canadian Agricultural Adaptation Program (CAAP). In Saskatchewan, this program is delivered by the Agriculture Council of Saskatchewan.






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  • Did you know that...
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