Aquatic Invasive Species: The Yellow Flag Iris

East Kootenay Invasive Plant Council (EKIPC) is seeking volunteers to remove yellow flag iris from a tributary of the Kootenay River.

East Kootenay Invasive Plant Council is hosts a volunteer Dig-it Day at Skookumchuck Sunday

East Kootenay Invasive Plant Council is hosts a volunteer Dig-it Day at Skookumchuck Sunday

When in bloom, the yellow flag iris (Iris pseudacorus), also known as pale-yellow iris, is a truly spectacular flower.  This large showy flower, whose native habitat is Europe, North Africa and warmer parts of Asia, is generally believed to be the source of the famous symbol of French monarchy: the Fleur-de-lis (Fleur-de-lys).  Directly from those French roots, the Fleur-de-lis is found on the flags of New Orleans and Quebec, both former French colonies.

But it is not the historical imagery related to this plant that makes it noteworthy.  Instead, the biology of this plant makes it unique.

Vigorous growth and large underground root and stem systems (rhizomes) mean the water-loving plant has been used successfully as erosion control and for rehabilitation.

According to the journal Water, Air, and Soil Pollution (1986), yellow flag iris was found to work as a living filtration system (biofilter), able to absorb heavy metal residues from water.  The yellow flag iris’ seeds are so well adapted to aquatic ecosystems that its seeds are like corks — completely buoyant in water, and able to float more than a year after being released, much longer than any other wetland species.

These adaptations make this introduced species a benefit for some, but a serious concern for biologists and wetlands in the Kootenays.  When introduced into marsh environments, the yellow flag iris will readily outcompete native species, resulting in dense stands of iris.  It is thought to reduce breeding and rearing habitat for a number of aquatic species like waterfowl and fish – including salmon.  And once introduced into an area, yellow flag iris is very difficult to remove and requires years of management and monitoring efforts.

For this reason, the East Kootenay Invasive Plant Council (EKIPC) is seeking volunteers in Skookumchuck at 1 pm on Sunday, Sept, 21, to assist local residents to remove yellow flag iris from a small tributary of the Kootenay River.  Unlike the West Kootenay, which has a number of large infestations of yellow flag iris, this small infestation is the only known yellow flag iris site in the East Kootenay and an important focus of eradication efforts.  With careful planning and a few extra hands, this small infestation should be successfully removed – preventing any further spread of this highly invasive water plant further down the creek and river.

Visit the PlantWise page on BC’s Invasive Species Council website for more information (

If you are interested in learning how to identify this invasive species or can help with removal efforts, contact Todd or Cathy at EKIPC ( or

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