The project investigated the effects of adding a mycorrhizal fungal inoculant on three plants species- two sedges and one tree – growing in stormwater biofilters. We evaluated the impacts on both plant establishment and on plant stress and pollutant removal after two durations of drought. We found that adding mycorrhizae had minimal impact on plant growth and stress tolerance of the tree species, Melaleuca ericifolia, and had a similar impact on sedge species. Interestingly, different species reacted differently to inoculant addition with regards to water quality improvement. Removal of nitrogen and phosphorus was improved with added inoculant in one of the sedge species, Ficinia nodosa, both before and after a 2-week dry period. These results show that mycorrhizal inoculants may be a promisingamendment to biofiltration systems for improving water quality, but are less likely to improve plant health and tolerance to drought.