Frequently Asked Questions

Plant Selections

How do I know what type of plant to use?

Filterra has created a plant list for each region that describes the sun exposure, hardy range, plant spread and height to help a client best select their plant species. We have also created hardy zone specific plant lists if clients are interested in selecting plants by hardy zones. These lists are preferred if you are already aware of the project site. 

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How many plant replacements have occured since Filterra began commercial sales?

With over 1,200 Filterra systems installed since 2003, less than 1 % of the Filterra plants have been replaced. Of all the plant deaths to date, the majority of them have been from physical damage due to mowers. A few plants have also been stolen. 

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What is the life expectancy of Filterra plants?

The plant should live to its life expectancy. The plant comes from the nursery with nutrients in the potting mix that help it through its establishment period. Overtime those nutrients are used up, but the plant constantly receives nutrients from the stormwater runoff that help maintain the health of the plant. Some plants are also very adaptable to their growing conditions, and the plants on our approved list meet this criterion due to their drought tolerance. There is no reason why a plant living in the landscape outside of a Filterra unit should live longer than the same plant in the Filterra.

We do not recommend plant heights more than 15-25 feet tall to prevent the Filterra unit from becoming root bound. We use plants with a shallow fibrous root system that do not exhibit an aggressive root system. The plant may not grow as fast because it does not receive regular doses of fertilizer to enhance growth rate like some landscape plants, but there are enough nutrients from stormwater runoff to provide sufficient nourishment to maintain plant growth and survival. As long as the units receive proper maintenance (usually twice a year), there should not be any factors causing plant death.

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What is the plants role in pollutant removal?

Through phytoremediation (the use of plants to remove pollutants through the uptake of nutrients and metals by plant roots into the biomass of the plant), contaminants are removed from stormwater runoff. Plants can accumulate metals in the cell tissue to make them less toxic. Nitrogen amd phosphorus are used by the plant to grow more cells. Organic matter is used as an energy source and metabolized into water and carbon dioxide. This means that as the plant grows or increases in biomass, so does the system’s capacity to capture and process more pollutants. 

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Quick Links

  • Request DAKit: Design assistance stormwater
  • Gallery of pollutant removal and stormwater treatment images
  • How the Filterra Stormwater Bioretention Management System works