Rain Gardens For Home Landscapes
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What Is a Rain Garden?
RAIN GARDENS FOR
Rain gardens are beautiful natural landscape features that require less maintenance and
fewer chemicals than lawns. Rain gardens capture runoff from impervious areas such
as roofs and driveways and allow it to seep slowly into the ground. Most importantly,
HOME LANDSCAPES
rain gardens help preserve nearby streams and lakes by reducing the amount of runoff
and filtering pollutants.
Why Plant a Rain Garden?
Rain gardens provide for the natural infiltration of rainwater into the soil. This helps to
filter out pollutants including fertilizer, pesticides, oil, heavy metals and other chemicals
that are carried with the rainwater that washes off your lawn, rooftop and driveway. Rain
gardens also reduce peak storm flows, helping to prevent stream bank erosion and
lowering the risk for local flooding. By collecting and using rainwater that would other-
wise run off your yard, rain gardens allow you to have an attractive landscape with
less watering.
How Do Rain Gardens Work?
A rain garden receives runoff water from roofs or other impervious (hard) surfaces such
as driveways. The rain garden holds the water on the landscape so that it can be taken
in by plants and soak into the ground instead of flowing into a street and down a storm
drain or drainage ditch. The plants, mulch and soil in a rain garden combine natural
physical, biological and chemical processes to remove pollutants from runoff. Many
pollutants will be filtered out and break down in the soil over time.
Water should stand in a rain garden no longer than 24 hours after the rain stops. Mosquitoes
cannot complete their breeding cycle in this length of time, so a rain garden should not
increase mosquito populations.
40 Courtland Street, NE
Special thanks to Rose Mary Seymour, Ph. D., P.E. of the University of Georgia, College of
Atlanta, Georgia 30303
Agricultural and Environmental Science, Biological and Agricultural Engineering, Griffin Campus,
UW-Extension Office, the Pollution Prevention Assistance Division (P2AD), Alfred Vick, ECOs
Environmental Designs and Maplewood, Minnesota (for photos).
WWW.CLEANWATERCAMPAIGN.COM
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Where Are The Best Places to Locate Rain Gardens?
What Plants Should You Use?
A rain garden should be curvy in shape and is best situated with the longest length perpendi-
cular to the slope of the land.
Rain gardens are best located in nat-
Use rope to lay out the boundary of the rain garden.
Finding plants for your rain garden is not diffi-
ural depressions (low lying areas where
cult. Many well-suited plants are available at your
3. Once the rain garden is laid out, you can start digging.
water flows naturally). They should
nearest landscaping supply store. Here are some
be sited at least 10 feet from a house
Begin by removing soil in the rain garden so
suggested plants (common and scientific names):
or building. While they should not be
that the deepest part is about 8 -10 inches
deep.
next to building foundations, rain
Trees
gardens near impervious surfaces such
The bottom of the rain garden should be as
Trees are effective in rain gardens that are larger than
as driveways, patios and sidewalks
level as possible so some minor grading
150 square feet. Plant trees at least eight feet apart.
may be necessary.
help capture the runoff from these areas.
Bald Cypress
Taxodium distichum
The extra soil removed from the rain garden
Black Gum
Nyssa sylvatica
Sites with steep slopes (an elevation
should be used on the downhill side of the
Crape Myrtle
Lagerstroemia indica
change of more than 12 feet down
garden to create a berm, an earthen dam or
Fringetree
Chionanthus virginicus
barrier that will keep the water in the rain
per 100 feet in length) may not be
Green Ash
Fraxinus pennsylvanica
garden. The top of the berm should not be
suitable for rain gardens. Further, if you have a septic system, avoid planting a rain garden
Musclewood/American Hornbeam
Carpinus caroliniana
higher than the uphill edge of the rain garden
over the top of the drainfield. It is recommended that a landscape professional be con-
Red Maple
Acer rubrum
(no more than 12 inches high). The rain
sulted if you plan to build a rain garden larger than 300 square feet.
garden should be designed to hold no more
River Birch
Betula nigra
than 6 inches of water above the ground surface.
Sweetbay Magnolia
Magnolia virginiana
Willow Oak
Quercus phellos
4. Mix organic matter into the soil within the rain garden by spreading 2 to 4 inches
Witch Hazel
Hamamelis virginiana
Where Are Rain Gardens Not Beneficial?
of compost over the area and mixing the organic matter in with the existing soil.
Shrubs
If the soil is acidic (has a low pH), add lime to neutralize the pH of the soil. Contact a local
American Beautyberry
Callicarpa americana
University of Georgia Cooperative Extension Service office for a soil sampling test by calling
Bottlebrush Buckeye
Aesculus parviflora
Rain gardens are not appropriate where the seasonal high water table is
770-228-7274 or go online to www.ces.uga.edu.
Buttonbush
Cephalanthus occidentalis
within 24 inches of the soil surface because the water table will prevent
For soils with high clay content, it may be beneficial to remove about 1-2 feet of the soil
Common Winterberry/Winterberry Holly
Ilex verticillata
infiltration.
and replace it with a more porous “rain garden soil.” A soil mix suitable for rain gardens is
Inkberry
Ilex glabra
50-60 percent sand, 20-30 percent topsoil, and 20-30 percent compost. The clay content in
Oakleaf Hydrangea
Hydrangea quercifolia
Rain gardens should not be placed over a septic system.
the rain garden soil replacement mix should be no more than 10 percent.
Rose of Sharon
Hibiscus syriacus
Rain gardens should not be located next to building foundations.
Summersweet Clethra
Clethra alnifolia
5. A shallow swale or corrugated drain pipe should be set up to carry the water from the
Virginia Sweetspire
Itea virginica
roof downspout to the rain garden.
Wax Myrtle
Myrica cerifera
Make sure that the ground slopes away from the house so that water does not collect
How To Create a Rain Garden
around the foundation.
Perennials, Grasses and Groundcovers
Asters
Aster spp.
6. Establish a grass or groundcover border along
Blackeyed Susan
Rudbeckia hirta
the upper edge of the rain garden to slow
1. Locate a site for a rain garden in a natural
Blue Lobelia
Lobelia siphilitica
down the runoff water as it enters the rain
depression in the landscape.
Broadleaf Uniola/Indian Woodoats
Chasmanthium latifolium
garden, and do the same over the berm to
Broomsedge
Andropogon virginicus
2. Determine the size and shape of the
stabilize it as a border of the rain garden.
Cardinal Flower
Lobelia cardinalis
rain garden.
Cinnamon Fern
Osmunda cinnamomea
7. Select and plant drought tolerant, wet toler-
Clubed Begonia
Begonia cucullata
To calculate the size, consider the area
ant and hardy plants. A mix of ornamental
Golden Ragwort
Packera aurea
draining to a rain garden, including the
grasses, shrubs and self-seeding perennials
Goldenrod
Solidago flexicaulis
roof area or impervious area that drains
Ironweed
Vernonia noveboracensis
are good choices. See chart of plants.
to the downspout and the area of land
Joe-Pye Weed
Eupatorium fistulosum
between the downspout and the rain
Liatris
Liatris pycnostachya
8. Once plants are in place, cover the garden
garden. The larger the roof or impervious
Narrowleaf Dragonhead
Physotegia angustifolia
(hard) area and the slower that water infil-
with a 3” layer of mulch. Lighter mulches such as pine bark and straw will float in
New England Aster
Aster novae-angliae
trates into the soil, the more area of rain garden needed.
water and may be washed away to the edges of the rain garden. Better mulch choices
Red Columbine
Aquilegia canadensis
for a rain garden are more dense materials such as pine straw, wood chips or shred-
An effective rain garden depends on water infiltrating into the soil of the garden. Soils with
Royal Fern
Osmunda regalis
a lot of clay will infiltrate water very slowly, so the size of a rain garden in clay soils should
ded wood.
St. John’s Wort
Hypericum fasciculatum
be 60 percent of the total drainage area. Sandy soils infiltrate water more quickly, so a rain
Scarlet Rosemallow/Swamp Hibiscus
Hibiscus coccineus
garden in a sandy location does not need to be as large. For sandy soils, the rain garden
9. To maintain your rain garden, remove weeds on a regular basis as the landscape plants
Swamp Milkweed
Asclepias incarnata
size should be about 20 percent of the area draining to it. Loamy soils can be sized some-
grow, and replenish mulch as needed.
Swamp Sunflower
Helianthus angustifolius
where between 20 and 60 percent, keeping in mind that the slower the infiltration, the larger
Switchgrass
Panicum virgatum
the area should be. It is important to know your soil before you start a rain garden project.
As the plants in the rain garden mature, there will be less need for mulch and weeding.
Wild Ginger
Asarum canadense
To test the infiltration of your soil, dig a hole 6-8 in deep in the area that the rain garden
Yellow Stargrass
Hypoxis spp.
Rain gardens should be relatively low maintenance if the correct plants are chosen.
will be located. Fill the hole with water. Observe how long it takes for the water to move
(infiltrate) into the soil. If any water stays in the hole for 12 hours or longer, then the soil is
For help in finding a location to purchase native plants, go to the Georgia Native Plant
not suitable for a rain garden.
10.IMPORTANT NOTE: Plan on providing an “overflow” path for water to take if the
Society’s website at www.gnps.org.
If you determine that your rain garden area needs to be greater than 300 square feet and you
rain garden fills and more rain comes. This path should be stabilized with a hardy
wish to plan the site without outside assistance, divide the drainage area between two or
grass or groundcover.
An additional list of plants suitable for rain gardens can be obtained through the University of Georgia Cooperative Extension
more rain gardens, and build each so you can easily manage them both.
Service. The bulletin, called “A Compilation of Low-Maintenance Plants for Georgia Landscapes” (H-91-009), lists both native
and non-native plants that are drought and moisture tolerant. The bulletin can be found at a local extension office or online
at www.ces.uga.edu.
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