March 14, 2007 | By: Laura Skillman

Rain gardens are an environmentally friendly option homeowners have for reducing storm water runoff from their property while creating an aesthetically pleasing spot in the landscape.

Storm water runoff poses an increasingly difficult problem for many urban areas. Storm sewers, drainage ditches and retention basins often overflow during significant rains, causing soil erosion and flooding. Runoff can also carry excess fertilizer and pesticide residue to streams and lakes that compromise their ecological balance. Most commercial properties are now required to develop storm water management plans, but developing a rain garden is something the average homeowner can do as well.

A rain garden is a strategically located low area planted with native vegetation that intercepts runoff and allows it to infiltrate the soil, said Rick Durham, consumer horticulture specialist with the University of Kentucky College of Agriculture. Rain gardens are becoming popular in many parts of the Midwest and some municipalities offer tax credits to properties where they are installed. Durham said he was not aware of any incentives available to Kentucky homeowners.

Rain gardens are not bogs or marshes, rather they are constructed to collect runoff and allow it to drain away within a few days, he said. Rain gardens do not promote the growth of mosquitoes.

Durham and Jim Lempke, curator of natural ecosystems at The Arboretum, say interest in rain gardens is growing. Both have given presentations in recent months to various horticultural groups on these gardens.

“I’m talking with people about them a lot, but I’m not sure how many are being installed,” Durham said.

Anyone that wants to see one can do so by visiting the Bluegrass collection located near the woods at The Arboretum, Lempke said. Many plants suitable for rain gardens can also be found throughout the facility. 

Most residential rain gardens are 100 to 200 square feet in size, which is large enough to handle the runoff produced from a typical roof in an average rain, perhaps a thousand gallons of water, Durham said. 

The rain garden is located down slope and away from the building so that wet soil will not compromise the structural integrity of the building’s foundation. A naturally occurring low lying area is ideal for the rain garden, but a shallow depression can be constructed by excavating some soil and creating a small bank or berm on the lower side of a slope, he said. 

Check the area for proper drainage by digging a hole one foot deep and one foot wide and filling it with water, Durham said. If the water drains away within 24 hours, drainage is adequate. If drainage is not adequate, loosen the soil and mix in additional sand and compost or peat moss to aid drainage.

When designing a rain garden, Lempke suggests selecting native plants with vivid flowers and making grasses and sedges the “backbone” of the garden.

Many native perennial plants do very well in rain gardens. Some of the more popular plants might include Joe Pye weed, black-eyed Susans, asters, goldenrod, and swamp milkweed, Durham said. Though not necessarily native, ornamental grasses also work well in rain gardens as do several varieties of native shrubs such as button bush, beautyberry, bottlebrush buckeye, and oakleaf hydrangea. 

Other species that are suitable include box elder, swamp white oak, red maple, swamp rose mallow, pale dogwood, sneezeweed, wild sunflowers, cardinal flower and ladies’-tresses, Lempke said. 

There are a large number of plants suitable for rain gardens and with a little research, homeowners can find the right ones for their landscape. 

Some other suggestions from Lempke to aid the environmental and aesthetic benefits of a rain garden are to be sure to keep native plant gardens looking neat. A homeowner can also add “cues that show care” such as a strip of mowed turf, fences, stone walls and neat rows of wildflowers.

The gardens also can be planted adjacent to existing trees and shrubs that may be providing cover and food for wildlife. If installing a rain garden near an existing tree or shrub, take care to avoid extensive changes in grade that may occur. Many tree roots are quite sensitive to even a few inches of extra surface soil. Keep the view to your front doors and windows open, he said, and use tall plants and shrubs to frame the public view to your house rather than to cover it.

Spring and fall are good times to install a rain garden. Anyone wanting more information can contact a county office of the UK Cooperative Extension Service or submit their questions to was developed by the Cooperative Extension Service to provide gardeners, consumers and other visitors a reliable source of updated horticultural information through a database of commonly asked gardening questions that have science-based, peer-reviewed answers.

There will also be a workshop this spring at The Arboretum for anyone interested in rain gardens. The program is May 10 from 9 a.m. to noon. Topics discussed will include basic processes of storm water movement, appropriate native plant species, garden patterns and structural materials.

Later this spring, The Arboretum and Lexington will be installing a large rain garden near the Glendover Road entrance as part of a joint storm water project.


Rick Durham, 859-257-3249, Jim Lempke, 859-257-9339