Marcy-Holmes Neighborhood
Rainwater Resource Recycling
Demonstration Project

Rain Gardens

Definition

• Shallow (2"-18") depressions, typically planted with colorful native plants, strategically located to collect, infiltrate and filter rain that falls on hard surfaces like roofs, driveways, alleys, or streets to minimize negative impacts of excessive runoff from these surfaces on lakes and streams.

Components

• Plants: Any plants that can tolerate alternating wet and dry conditions will work. Because native plants have roots up to 15’ deep, they are especially well suited for collecting, infiltrating and filtering rain. Additionally, native plants require the least maintenance and maximize wildlife habitat quality.
• Compost: Added to increase soil organic matter content if needed
• Sand: Added to increase soil infiltration capacity if needed.
• Mulch: Shredded hardwood mulch helps keep moisture in the soil between rain falls, builds up the soil, protects the soil from erosion, keeps the soil from sealing up, and helps keep weeds out of the garden.
• Edging: 6" Deep edging will help keep turfgrass from invading the rain garden.

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Advantages/ Rationale/ Benefits

• Increases amount of rainfall that infiltrates into the ground, which recharges groundwater and helps sustain base flows in streams during dry times.
• Reduces downstream flooding, reduces lakeshore and streambank erosion, and mitigates negative impact on water quality of downstream surface waters by reducing stormwater runoff.
• Reduces need for costly traditional stormwater management structures.
• Aesthetic amenity rich in regional character (if using native plants).
• Wildlife habitat value.
• Low maintenance.

Typical Costs

Material costs for a 100 square foot rain garden: $200 +/-

Installation

Installation of a rain garden is no more complicated than installing a perennial garden. For detailed guidance, see any of the following web sites:

• http://www.ci.maplewood.mn.us/PublicWorks/RainWater%20Garden/RAINWATER%20GARDENS.htm
• http://www.ci.maplewood.mn.us/vertical/Sites/{EBA07AA7-C8D5-43B1-A708-6F4C7A8CC374}/uploads/{27BFF8A2-982E-4D6A-A7A1-319BA2180EE2}.PDF
• http://clean-water.uwex.edu/pubs/raingarden/gardens.pdf
• http://www.mninter.net/%7estack/rain/

Maintenance Requirements

Watering

Watering is critical the first weeks after planting. Plants will need about one inch of water per week. In sandy soil, watering every 2 to 3 days is recommended, as sandy soils drain rapidly. Once the plants are established, they develop deep roots (up to 15’ deep in some species) and can withstand short periods of drought.

Weeding

Weeding is also critical during the first year of establishment. Once the native plants are mature and their roots are fully developed (2-3 years after planting), required weeding will be minimal as the native plants will be able to outcompete most weeds.

Fertilizing

Fertilizing is not recommended for native plantings, unless soils are extremely nutrient deficient. Because native plants are adapted to local soils and do not benefit from additional nutrients, fertilizing native plantings mainly stimulates stronger weed growth.

Spring Cleanup

To enjoy the rich colors and textures of native plantings throughout the winter, wait until spring to cut back dead vegetation to clean up the garden for the new season. Waiting until spring to cut back the vegetation also maximizes wildlife value and self-seeding.

Mulch

Topping off the mulch every few years to maintain a 3" layer of mulch on the rain garden will help minimize weed growth and build up the soil.

Marcy-Holmes Neighborhood Rain Garden Demonstration Sites (see walking tour link for map)

• Rollins Court Condominium Complex, northeast corner of SE 14th Ave and SE 7th St.:

Rain garden collects stormwater from adjacent parking lot (click to enlarge)	Before rain garden installation - unused turf grass ideally located for conversion to rain gardens combining stormwater utility function with aesthetic amenity
Volunteers installed the Rollins Court Rain Gardens on August 26, 2003	Two weeks after rain garden installation - stormwater runoff from adjacent parking lots soaks into the rain gardens within hours of storm, helping to alleviate excess stormwater runoff burden on the Mississippi River

• Private residence at 1205 SE 7th St.
  Roof downspout directed to rain garden under ground

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• Private residence at S.E. 515 7th Ave.
  Roof downspout directed to rain garden above ground (garden installed prior to Marcy-Holmes Rainwater Resource Recycling Project)

• Andrew Riverside Park Rain Gardens: North corner of 4th St SE and 8th Ave SE
  Site runoff flows above ground to several rain gardens. Designed by Metropolitan Design Center with a grant from McKnight Foundation and constructed with a separate grant by MWMO

For more information: contact The Kestrel Design Group, Inc. at 952 928-9600 or tkdg@thekestreldesigngroup.com

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