RAIN GARDENS
Why are rain gardens important?
Why do you encourage homeowners to try and include one in their yard?
Where do they work best and why?
Tips for creating one.
What is a Rain Garden?
A Rain Garden is an attractive landscape feature designed to capture, filter, and infiltrate
stormwater back into the soil rather than running off your property or causing erosion. Rain
gardens are landscaped areas that treat stormwater run-off. They are built as shallow depressions
(basins) in the ground that are filled with good draining soil mix and beautiful plants that can
tolerate wet soil and periods of drought.
As water collects in the rain garden, it is filtered and slowly absorbed by the soil and plants. The
soil and roots of the trees, shrubs and perennials planted in the rain garden, filter pollutants,
pesticides, and herbicides from the rainwater. Well-designed rain gardens will hold water for no
longer than 24-48 hrs. The rainwater is often soaked into the ground within a few hours after a
typical rain event. These systems help to replenish ground water and helps improve the quality of
water entering our nearby drains and streams.
Why are rain gardens important?
When it rains, water falls on roofs, driveways, lawns, between houses, over parking lots and
through storm drains. As stormwater travels over these surfaces, it collects pollutants, pesticides,
herbicides, sediment and pet wastes. Seventy percent (70%) of pollutants in our streams, rivers
and lakes are carried there by stormwater. Most people do not know that about half of the
pollutants are caused by what we do in our gardens and yards.
Planting a rain garden might seem like a small part of stormwater management, but if you calculate
the amount of rain that runs off you roof, you might be very surprised. Water running off a house
roof can be channeled into a rain garden, rather than heading into the street to a storm drain
carrying pollutants with it.
In undisturbed landscapes, such as woods and open field, there is very little stormwater run-off
because rainwater filters down through the soil or evaporates into the atmosphere.
When we build houses and communities, we compact soils, install impervious surfaces (buildings,
driveways and sidewalks), and remove trees and native vegetation resulting in an increase in
stormwater runoff. As a homeowner, we can help decrease water runoff by installing water quality
structures like a rain garden, and rain barrels.
Carol Fryer, VCE Master Gardener
February 17, 2014
Where to build a rain garden?
A rain garden should be at least 10 ft. from a house so water soaking into the soil does not seep
into the foundation. Do not place the rain garden directly over a septic system, or underground
utilities.
A wet area of your land may not be a good spot since the infiltration is poor there. An area closer
to the runoff source (roof, driveway) to intercept the water is a better choice.
If your water table is high, less than 2 feet deep from the surface, a rain garden will not work since
infiltration is an issue.
Locate a rain garden in sun or partial sun, not directly under a big tree.
Placing the rain garden in a flatter part of a yard makes digging much easier.
A slope of less than 12% grade work best since the base of the rain garden must be level, and less
incline requires less filling in of the downward side of a slope.
TIPS:
* Call your County Stormwater Division or Virginia Cooperative Extension Office/Master Gardeners
to find out if they have programs or information to help homeowners.
* Ask if there are any rain gardens installed in public places that you can visit.
* Call Ms. Utility (811) before digging near your house.
* Look at your land and home, and note where the rain runs off during a rainstorm.
* Get a soil test to determine the make-up of your soil
* Do an infiltration test at the site for the rain garden to see how quickly water seeps into your soil.
* To determine size of your rain garden, calculate how much rain flows to the area for your rain
garden based on size of impervious surfaces (roof, driveway, sidewalk) and pervious surfaces
(lawn). (Formulas are available in homeowner guides online, such as the VA Dept. of Forestry
booklet.)
* Before you dig, lay out a water hose to the dimension and shape desired of your rain garden to
get a sense of what it will look like, and adjust the shape until it is pleasing to you.
* Research native plants that might work for you, and locate nurseries where they are available.
* Lists of native plants and other plants that are particularly suited for rain gardens are available
online. Universities, and State government websites are good choices to use
(rain gardens site: edu or rain gardens site:gov).
Benefits to you
A rain garden will increase the beauty of your yard, help prevent pollution from reaching our
streams, reduce the cost of stormwater management, decrease amount of time and money put into
maintaining a lawn, improve ground water re-charge, and help clean water in your neighborhood.
A slogan from Arundel County, MD :
When it Rains, It Drains – Reduce runoff,
Slow it Down,
Spread it Out,
Soak it In
Carol Fryer, VCE Master Gardener
February 17, 2014
References/resources:
* Rain Garden Resources - James City County, online information and video
* Rain Garden Plant, Virginia Tech, pubs.ext.vt.edu/426/426-043/426-043_pdf.pdf
* VA Dept. of Forestry Rain Gardens, www.dnr.state.md.us/forests/pdfs/VA_RainGardens.pdf
* Rain Gardens of West Michigan, www.raingardens.org
* Fairfax Virginia Rain Garden Booklet –online
* Rain Gardens in Coastal Maryland’s Coastal Plain - online
Books:
* Rain Gardens – Sustainable Landscaping for a Beautiful Yard and a Healthy World, 2012,
Lynn Steiner and Robert Dumm
*Rain Gardening in the South, 2009, Helen Kraus and Ann Spafford
* Rain Gardens , Managing water sustainability in the garden and designed landscapes, 2007
Nigel Dunnett and Andy Clayden.
Carol Fryer, VCE Master Gardener
February 17, 2014