A rain garden is a shallow, planted depression designed to capture, filter, and infiltrate stormwater runoff. Using engineered soil and carefully selected plants, rain gardens can absorb up to 30% more water than conventional turfgrass while creating attractive, low-maintenance landscape features that attract beneficial wildlife.

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See the in Action

At the demonstration site, the rain garden receives overflow from the bioswale. Water enters through a rock apron inlet, spreads across the garden basin, ponds to a depth of approximately 6 inches, and then slowly infiltrates through 18 inches of amended rain garden soil mix. Three groupings of 18-inch boulders serve as rock features on the garden slopes, adding visual interest and helping dissipate water energy. A flat river rock apron at the outlet manages overflow during heavy storm events

Practice Type: Shallow bioretention / rain garden (surface infiltration and biofiltration)

Dimensions: Approximately 10 ft. diameter (80 sq. ft. area)

Ponding Depth: 6 inches

Soil Mix Depth: 18 inches (50–60% sand, 20–30% topsoil, 20–30% compost)

Cost Range: $10 to $15+ per square foot (materials and labor)

Water Flow: Receives overflow from the bioswale

Maintenance

Task
Frequency
Details

Prune and trim

Late winter (Jan. – Feb.)

Prune woody shrub plantings and trim back dead winter foliage

Divide plants

Spring

Thin or divide spreading overgrown plants

Mulch inspection

Spring

Verify mulch depth of 2–3 inches; add mulch as needed

Weed control

Spring and fall 

Pull weeds from rain garden and vegetated curb plantings

Drainage monitoring

Summer

Monitor for proper drainage (no standing water after 72 hours); irrigate in drought conditions

Creek bed vegetation

Late summer

Remove undesirable vegetation from dry creek bed by trimming or targeted herbicide

Erosion inspection

Fall

Visual inspection for erosion spots or missing plants; replace as needed

Sediment and debris

Late fall

Remove excess sediment, leaves, or debris at inlet and overflow outlet areas