A shallow depression planted with deep-rooted, native plants selected to tolerate both drought and inundation conditions and designed to treat and filter stormwater pollutants.
The sandy soils of biorentention areas, designed to infiltrate water within 24 to 48 hours of a typical rain event, can be challenging environments for plants to survive. Plant selections should be both drought and inundation tolerant.
Bottom of basin (in bioretention soils)
- Plants in bioretention areas will need to be selected based on MSD requirements.
- Smaller plants placed at tighter spacing than typically specified will ensure a functioning biorentention area, limit weed pressures, and reduce problems associated with erosion and soil migration.
- Plants selected should be extremely hardy and tolerant of extended periods of dry conditions.
- Trees can be used in bio-retention basins, but sized appropriately for the overall space and space of the rain garden.
- A planting buffer that extends a minimum of 3’-0” beyond the top of slope is required.
- Slopes should not exceed 4:1 for plant establishment.
- For ease of maintenance, turfed slopes will perform the best. Turf should be sodded, hydroseeded, or planted using pre-seeded coir rolls.
- Planted slopes can be utilized for aesthetic purposes, but additional care should be taken to ensure mulch and soils do not contaminate bioretention soils.
- Sediment socks or similar should be placed at the toe of slopes between mulched slope and bioretention area. These are to remain in place for one year, minimum depending on plant establishment.
- Slopes should be mulched with hardwood or compost mulch.
- On slopes in excess of 1:6, bio-degradabe anti-wash jute mesh should be used over the mulch surface to ensure that mulch does not float during high water event.
Bioretention Plant List
TREES AND SHRUBS
- WITCHAZEL Hamamelis virginiana
- SWAMP WHITE OAK Quercus bicolor
- BALD CYPRESS Taxodium distichum
- BLACK TUPELO Nyssa sylvatica
- SIDEOATS GRAMA Bouteloua curtipendula
- BUR SEDGE Carex grayi
- FOX SEDGE Carex vulpinoidea
- NORTHERN SEA OATS Chasmanthium latifolium
- LITTLE BLUESTEM Schizachyrium scoparium
- PRAIRIE DROPSEED Sporobolus heterolepis
- BLUESTARS Amsonia illustris
- COREOPSIS Coreopsis lanceolata
- PURPLE CONEFLOWER Echinacea purpurea
- IRIS Iris virginica, I. fulva
- BLACK-EYED SUSANS Rudbeckia fulgida
- GOLDEN ALEXANDER Zizia aurea
NOTE: Refer to MSD Bioretention Plant List for additional species recommendations.
Preferred Bioretention Planting
Enhanced Bioretention Planting