What Is a Rain Garden?

Homeowners in many parts of the country are catching on to rain gardens – landscaped areas planted with native vegetation that soak up rain water, mainly from the roof of a house or other building. A rain garden can be placed at any point along the runoff pathway in the landscape and in sun or shade. It is a shallow depression, only 6-8” deep. The rain garden fills with a few inches of water after a storm and the water slowly filters (for about 48 hours) into the ground rather than running off to a storm drain. Compared to a conventional patch of lawn, a rain garden allows about 30% more water to soak into the ground.

Why are rain gardens important? As cities and suburbs grow and replace forests and agricultural land, increased stormwater runoff from impervious surfaces becomes a problem. Stormwater runoff from developed areas increases flooding; carries pollutants from streets, parking lots and even lawns into local streams and lakes; and leads to costly municipal improvements in stormwater treatment structures. By reducing stormwater runoff, rain gardens can be a valuable part of changing these trends. While an individual rain garden may seem like a small thing, collectively they produce substantial neighborhood and community environmental benefits.

Rain gardens work for us in several ways:

• Increasing the amount of water that filters into the ground, which recharges local and regional aquifers;

• Helping protect communities from flooding and drainage problems;

• Helping protect streams and lakes from pollutants carried by urban stormwater – lawn fertilizers and pesticides, oil and other fluids that leak from cars, and numerous harmful substances that wash off roofs and paved areas;

• Enhancing the beauty of yards and neighborhoods;

• Providing valuable habitat for birds, butterflies and many beneficial insects.

Frequently asked questions:

Does a rain garden form a pond?
No. The rain water will soak in so the rain garden is dry between rainfalls. (Note: some rain gardens can be designed to include a permanent pond, but that type of rain garden is not addressed in this publication).

Are they a breeding ground for mosquitoes?
No. Mosquitoes need 7 to 12 days to lay and hatch eggs, and standing water in the rain garden will last for a few hours after most storms. Mosquitoes are more likely to lay eggs in bird baths, storm sewers, and lawns than in a sunny rain garden. Also rain gardens attract dragonflies, which eat mosquitoes!

Do they require a lot of maintenance? Rain gardens can be maintained with little effort after the plants are established. Some weeding and watering will be needed in the first two years, and perhaps some thinning in later years as the plants mature.

Is a rain garden expensive? It doesn’t have to be. A family and a few friends can provide the labor. The main cost will be purchasing the plants, and even this cost can be minimized by using some native plants that might already exist in the yard or in a neighbor’s yard. **

Downloadable Landscape Plans

Landscape expert Chris Hale and the Low Impact Development Center developed a series of simple, affordable landscape plans.

Although designed for Maryland, these plans can help guide and inspire design of rain gardens in Virginia. The plans are designed for certain physiographic regions - coastal, piedmont and mountain, so be sure to check the Virginia physiographic regional map found here if you are uncertain in which region you will be planting. A good number of the native plants specified also are native to Virginia. Please consult the Digital Atlas of the Virginia Flora to be certain. You may need to swap out a species or two.

Below are some examples of the many options:

Coastal Region

Butterflies Swale Low Maintenance Garden - 250 sq. ft.
Full Sun
Part Shade - Shade

Herbaceous Perennials Border Raingarden - 200 sq. ft.
Full Sun
Part Shade - Shade

Low Maintenance, Deer Resistant, Garden - 200 sq. ft.
Fall Sun
Part Shade - Shade

For the Birds Raingarden - 450 sq. ft.
Full Sun
Part Shade - Shade

Piedmont Region

Corner Raingarden - 150 sq. ft.
Full Sun
Part Shade - Shade

Entry Raingarden Walk with Flanking Pavers - 113 sq. ft. with 72 pavers
Full Sun
Part Shade - Shade

Hedgerow Raingarden
Full Sun, 900 sq. ft.
Part Shade - Shade, 903 sq. ft.

Trees and Shrubs Border Raingarden - 550 sq. ft.
Full Sun
Part Shade - Shade

Mountain Region

One Nice Tree - 192 sq. ft. 16’ x 12’
Full Sun
Part Shade - Shade

Low Maintenance Raingarden Deer Resistant - 200 sq. ft.
Full Sun
Part Shade - Shade

Butterflies Swale Raingarden - 250 sq. ft.
Full Sun
Part Shade - Shade

** Excerpted from Rain Gardens: A How-to Manual for Homeowners, by University of Wisconsin System. University of Wisconsin–Extension (out of print)

Slow Down, Spread Out, Sink In

In a rain garden, pollutants are filtered out of the water by the plants, soil and soil microorganisms. The clean water then infiltrates downward to recharge the groundwater aquifer; evaporates; evapo-transpires through the plants back up into the atmosphere; or is absorbed and used by the plants.

Native plants for rain gardens

When considering plants for a rain garden, remember that there are three planting zones: low (wettest), middle, and high (driest upper edge area). Select plants based on the zone. Additionally, choose plants based on the size of the garden and the mature size of the plants. Trees and larger shrubs may not be appropriate for smaller gardens, so consider herbaceous perennials and small, woody plants.

Possible Funding available for Homeowners

The Virginia Conservation Assistance Program (VCAP), a cost-share program for small Best Management Practices (BMP) retrofits, provides funding to citizens for the installation of 12 different practices, including rain garden installation. The BMPs primarily address stormwater runoff from roof, driveway and lawn. VCAP is administered through the Virginia Association of Soil and Water Conservation Districts and the local Soil and Water offices in the Chesapeake Bay watershed. Citizens may contact www.vaswcd.org to locate the nearest Soil and Water Conservation District office.

Planning to hire a landscaper?

The Chesapeake Bay Landscape Professional (CBLP) Certification is a voluntary credential system for professionals who design, install, and maintain sustainable landscapes. View a business directory of certified professionals at https://cblpro.org/.

Learn More about Rain Gardens and how to install

Rain Garden Technical Guide - Virginia Department of Forestry https://dof.virginia.gov/urban-community-forestry/urban-forestry-homeowner-assistance/rain-gardens/

Watershed Stewards Academy Rainscaping Manual - Anne Arundle Watershed Stewards Academy
http://aawsa.org/raingardens

RainScaping Campaign - an environmental partnership for stormwater runoff solutions for Anne Arundel County, Maryland. The site offers concepts for rain garden design and installation relevant to the whole Bay watershed. Remember native plants referenced in suggested rain garden designs may not be native to your region in Virginia, so check your Virginia regional plant list.
RainScaping with Rain Gardens (pdf)
The campaign is sponsored by the Chesapeake Bay Small Watershed Grants Program, which is administered by the National Fish and Wildlife Foundation.
http://www.RainScaping.org