Although leaf and stem growth provides no direct benefit for wastewater treatment, it is essential to provide energy for root systems necessary for the filter performance. Insect or disease damage should be investigated and may require corrective action. Select plants suitable for the site. Finding the right combination of plants that will work well in a particular rock-plant filter may take experimentation. A list of plant candidates is included in Rock-Plant Filter Design and Constructio n.
Some plants can tolerate more variation in water level than others.
Some are more tolerant of shade. Figures 3 and 4 show the variety of plants that can be used in rock-plant filters. If some of the plants are not thriving, consider other species. Invasive species may crowd out other plants in time. If more desirable plants are taken over by invaders, substitute less invasive plants.