Invasive Species Council of British Columbia

Field-based Workshop targets Yellow flag iris

Yellow flag iris (Iris pseudacorus) \ Credit: L Scott

November 25, 2022

In August 2022, ISCBC volunteers went to the Scout Island Marsh in Williams Lake to weed out Yellow flag iris (Iris pseudacorus), an invasive aquatic plant that grows in dense mats. It has a cheerful yellow flower, but its invasive habits leave much to be desired. It disrupts water flow and can reduce a marsh’s ability to purify water. This plant alters the ecosystem along the shoreline and can reduce the concentration of macroinvertebrates (insects) from 600 per m2 to 6 per m2. This has a rippling effect on the entire food chain that depends on these insects for survival. 

Led by Dr. Catherine Tarasoff, members of the Williams Lake Field Naturalists, Tsilhqot’in National Government Rangers, and ISCBC were given a presentation on Yellow flag iris and a field-based workshop treating a site at Scout Island. Key learning included identification of the species, whose leaves resemble those of cattail, and the science behind its ability to rapidly spread and survive. This hands-on experience gave participants the skills and background to continue monitoring and treating Yellow flag iris in the Cariboo region. 

Credit: E Cameron

“Visiting the site was interesting, because we treated an area here last year,” said Camille Sangarapillai, Cariboo Coordinator and Education Facilitator with ISCBC. “It can take as little as one year to completely treat a Yellow flag iris site and Dr. Tarasoff seemed happy with our treatment results.”  

The physical barrier – a large covering similar to a gym mat – will stay in place on the first treatment site, to be rechecked in early spring. 

The project is generously funded by the Habitat Conservation Trust Foundation 

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