| Stormwater runoff from urban environments can be mitigated by bioretention systems that capture stormwater and filter pollutants. Research has shown that vegetation improves the performance of these systems. Eight plant species were evaluated, four native to Michigan; Calamagrostis canadensis, Carex stricta, Pycnanthemum virginianum, Rudbeckia hirta, and four ornamental species; Calamagrostis x acutiflora 'Overdam', Carex muskingumensis, Pycnanthemum muticum, and Rudbeckia fulgida `Goldsturm' for use in bioretention sites. The study coupled a column experiment to evaluate species capabilities in removing common stormwater pollutants with a field study to evaluate growth performance under bioretention conditions. In the column experiment, Rudbeckia fulgida `Goldsturm' exhibited increased removal of nitrate, orthophosphate, total nitrogen, and total phosphorus over Rudbeckia hirta. Calamagrostis, Carex, and Pycnanthemum, native and ornamental species were similar in nutrient removal from stormwater. No differences were found between the native and ornamental species for metal uptake into plant tissue. The field study to determine percentage plant cover was conducted in 2012 and 2013 in a bioretention basin on the campus of Michigan State University East Lansing, MI. Both native and ornamental Calamagrostis and Pycnanthemum achieved 100% cover in all plots. The Carex muskingumensis outperformed Carex stricta. Rudbeckia hirta failed to reemerge in 2013 and Rudbeckia fulgida `Goldsturm' was unable to survive a period of flooding. Overall, these results indicate that plant selection for performance in bioretention applications should not be based on native status. |
