Nitrogen and Phosphorous Removal by Ornamental and Wetland Plants in a Greenhouse Recirculation Research System

A nutrient recirculation system (NRS) was used to assess the ability of four ornamental and three wetland plant species to remove nitrogen (N) and phosphorous (P) from stormwater runoff. The NRS was filled with a nutrient solution with total N and P concentrations of 11.3 and 3.1 mg.L(-1), respectively, to simulate high levels of nutrient contaminations in stormwater. Nutrient removal abilities of herbaceous perennial ornamental plants, canna (Canna xgeneralis Bailey) 'Australia', iris (Iris pseudacorus L.) 'Golden Fleece', calla lily [Zantedeschia aethiopica (L.) Spreng], and dwarf papyrus (Cyperits haspan L.) were compared with those of wetland plants arrow arum [Peltandra virginica (L.) Schott], pickerelweed (Pontederia cordata L.), and bulltongue arrowhead (Sagittaria lancifolia L.) in three experiments. 'Australia' canna had the greatest water consumption, total biomass production, and aboveground N and P content followed by pickerelweed. 'Golden Fleece' iris had higher tissue N concentrations than canna but much lower biomass production. Dwarf papyrus had similar total biomass as pickerelweed but less shoot biomass. N and P removed from the NRS units planted with canna (98.7% N and 91.8% P) were higher than those planted with iris and arrow arum (31.6% and 31.5% N, and 38.5% and 26.3% P, respectively). NRS units planted with dwarf papyrus had similar nutrient recovery rate as pickerelweed, but much less total N and P were removed as a result of less water consumption. The NRS units planted with calla lily had lower nutrient removal than canna and pickerelweed. Our results suggest that canna is a promising ornamental species for stormwater mitigation, and harvesting the aboveground biomass of canna can effectively remove N and P from the treatment system. However, more research needs to be done to evaluate factors that might affect plant performance in a floating biofiltration system.