Ask Mr. Smarty Plants

Common swales are typically vegetated with turf grass and are a conveyance tool, basically a grassy stormwater sewer that conveys water as quickly as possible from Point A to Point B. A bioswale differs in that the turf grass is replaced with native prairie vegetation. This will significantly reduce the flow velocity (slow down of the runoff) in the swale’s drainage course. The residence time of the runoff is thus increased, which gives it the time to be stored, filtered, and infiltrated. These processes remove pollutants and suspended solids from runoff.

We found this information on bioswale construction from the USDA, which shows compost tilled into the native soil (clay, in this instance) to facilitate the drainage. These are plants with fibrous roots that will hold in the soil when water is rushing by, help to slow it down, and permit the pollutants in the water to be filtered out. 

Since our suggestions are basically for prairie grasses, you might be interested in reading our How-To Article Recreating a Prairie, which has instructions for time of year to be planting, preparing the soil, planting and caring for the grasses. When you are ready to begin, go to our Native Plant Suppliers section, put your town and state in the Enter Search Location box, and you will get a list of native plant nurseries, seed companies and landscape consultants in your general area who can help you select the right plants for your purpose.

We found eight grasses native to the Orange County area that we believe fit your specifications. Follow the links to each individual plant webpage to learn expected height, season, etc.

Native grasses for bioswale in Southern California

Bromus ciliatus (fringed brome)

Juncus torreyi (Torrey's rush)

Nassella viridula (green needlegrass)

Phragmites australis (common reed)

Schoenoplectus tabernaemontani (softstem bulrush)

Typha latifolia (broadleaf cattail)

Andropogon glomeratus (bushy bluestem)

Muhlenbergia richardsonis (mat muhly)

Bromus ciliatus

Juncus torreyi

Nassella viridula

Phragmites australis

Schoenoplectus tabernaemontani

Typha latifolia

Andropogon glomeratus

Muhlenbergia rigens