The native species of cattails in Canada is Typha latifolia. Although the native species can form large monocultures, it is limited to depths of less than 25 cm. By comparison, the exotic, Typha angustifolia, or the hybrid, Typha glauca, can tolerate depths of up to 1.5 m. T. angustifolia spread from the eastern seaboard of North America inland to the Great Lakes in the late 19th century and continued its invasion further westward in the 20th century. Distribution maps show the species reached the Rainy River area by at least the mid 1980’s. The exotic cattails occupy the same niche as wild rice with the advantage of being a perennial and thus able to usurp the annual wild rice, particularly when water levels increase from year to year. This invasive species has had devastating effects on the wild rice stands in Rainy Lake.
The Seine River First Nation (SRFN), with their partners at Lakehead University, began control experiments for cattails on Rat River Bay in Rainy Lake. A cutting bar apparatus was attached to the front of the SRFN’s airboat (Figure above). The culms of the cattails were cut at the sediment:water interface in the fall of 2014. The theory to the procedure is that removing the culms stops the flow of oxygen to the rhizomes in the anaerobic sediment in winter, killing the plants.
Cattail removal proved to be remarkably effective. In the areas that were cut, the cattails were completely eliminated (Figure below). Additionally, the native species that were present in the cut areas (water lilies, soft stem bulrush) were not affected and since these species were in low density, they had little effect on wild rice production. Adding to the success of the procedure, wild rice apparently remained viable in the seed bank in the area previously occupied by cattails. The cut areas were completely filled with wild rice without seeding being required (Figure below).
Sequence of cattail cutting trial on Rat River Bay, Rainy Lake. Upper left: prior to cutting cattails. Upper right: after cutting, Fall 2014. Lower right: Spring, 2015 with rice in floating leaf stage (and no cattails). Lower left: re-established rice stand, Fall 2015. (Credit: P. Lee/J. Kabatay).
The success of these trials has prompted the SRFN to consider methods to expand control of the cattails on a large scale. These control efforts are absolutely critical or hundreds of hectares of wild rice on Rainy Lake will be eliminated by this invasive nuisance species. To access the full report, select Study #37 at: http://ijc.org/en_/RNLRCSB/Background_Report
Special thanks to Dr. Peter Lee, Lakehead University, for this summary.