As cities develop, more land is converted into impervious surfaces, which do not allow water to infiltrate. Careful urban planning is needed to ensure that the hydrologic cycle and water quality of the catchment areas are not affected. There are techniques that can attenuate peak flow during rain events and reduce the amount of metals, nutrients, and bacteria that enter the urban water cycle. This brief gives a short introduction on bioretention systems and documents the effectiveness of some 36 plant species in removing water pollutants. A summary on the maintenance requirements is also presented.