Rain Gardens

Sarah J. Williams

UMass Amherst

Sustainable Sites- Spring 2011

What Is a Rain Garden?

A garden with a shallow depression which is strategically located on a property to capture storm water runoff from impermeable surfaces-rooftops, patios, driveways etc, before it enters the waterways

The runoff water is held by the garden and allowed to slowly infiltrate the soil. The soil and plant roots naturally filter pollutants and reduce runoff.

Benefits

Allows a natural cleaning process to occur before the water reaches open waterways.

Protects communities from flooding.

Protects streams and lakes from pollutants .

Enhances beauty of landscaping.

Provides habitat for birds, butterflies and other good insects.

Makes for a good family/group project and encourages active green living.

Choosing a Location

10 feet from house to prevent seepage.

Near existing downspout.

Away from septic tank.

Away from existing wet patches-prevents ponding.

Sun is better than shade.

Flat is better than sloped.

Near a window or outside deck for viewing enjoyment.

Size and Shape

Garden should be 4-8 inches deep and as level as possible.

Size-

Rain Garden Area = 5-10% Surface area of runoff collection (i.e. roof, driveway etc)

Depth and area are dependant on climate in area where garden is being planted

Best to use visually pleasing shapes- round edges, kidney shaped etc.

Soil Requirements

Type of soil- sandy soil absorbs water faster than clay soil.

Compost makes a significant difference in root development.

TEST DRAINAGE FIRST -Dig a hole 18 inches deep and fill with water. If water is drained within 24 hours location is good for rain garden.

Plants

Use native plants in a variety of colors, shapes and sizes.

Select plants with a well-developed root system. Seeds can take too long to develop and can be compromised by too much water or animals.

Plants need to be able to handle heavy amounts of water and periods of dryness.

Plants that can handle more water should be placed at the lowest point in the garden- center or back edge depending on slope.

New England Wild Flower Association Rain Garden Plant List

If you are outside of New England, Google “rain garden plants for Your Location” to find plant lists.

New England Aster

Coneflower

Last But Not Least…

Maintenance

Minimal regular maintenance required.

Weeding: First year- once a month

during growing season

subsequent years- once a season

Watering only required during times of drought.

Cost

Relatively inexpensive project.

If its possible to get plants from friends or neighbors the cost will be negligible.

Plants purchased from a local nursery the garden will cost approximately $3-5 per square foot of garden.

Help Protect Your Watershed By

Planting a Rain Garden

Sources

• http://www.newenglandwild.org/publications-and-resources/rain-gardens.html

• http://learningstore.uwex.edu/assets/pdfs/GWQ037.pdf

• http://www.neponset.org/raingarden.htm

• http://www.ehow.com/how_5289060_test-soil-drainage.html