Rain gardens are areas of the landscape designed to catch rainwater long enough to allow it to percolate slowly back into the groundwater rather than run off the soil. Rain gardens help recharge groundwater, improve the water quality of streams and rivers, reduce flooding, and provide cover for wildlife and butterflies.
Rain gardens can be just shallow depressions of a few inches or elaborately constructed sites, depending on available space and needs of the site. The garden’s topography should be designed to encourage water flow into the garden. The site must drain well enough to allow slow and steady percolation into the groundwater. Soil drainage can be greatly enhanced by additions of finished compost in preparing the area.
Ideally, the rain garden should be located away from (10-foot minimum) and a bit below the grade of structures, such as the house, toolshed and garage. Rain barrels can be used to collect runoff water from house drainpipes and redirect to the rain garden. Reasonably level land will be much easier to work with.
Avoid placing the rain garden over a septic drain field or tank; a buffer of at least 50 feet is recommended. Be aware of shallow utilities in the area, and always call to locate and mark these utilities before you dig. Also avoid the edges of steep slopes where erosion is a risk.
As you consider the overall landscape design and appearance, like other gardens, you’ll need to consider the mature size, growth habit, flowering, fruiting and other characteristics of your plant selections. Most rain gardens feature moisture-tolerant perennial flowers, native wetland or wet prairie wildflowers, and grasses, but shrubs and trees can be used in larger gardens. Keep in mind that plants will also need to be tolerant of periodic dry spells as well as heavy rains.
The following are a few species to consider for your rain garden planting, but it’s by no means an exhaustive list.
Grasses
Big Bluestem
Indiangrass
Little Bluestem
Various Sedges
Flowers
Aster
Black-Eyed Susan
False Indigo
Flag Iris
Goldenrod
Great Blue Lobelia
Ironweed
Joe Pye Weed
Liatris
Penstemon
Swamp Milkweed
Shrubs
American Beautyberry
Arrowwood Viburnum
Bottlebrush Buckeye
Buttonbush
Oakleaf Hydrangea
Summersweet Clethra
Sweetspire
Trees
Bald Cypress
Fringetree
Ginkgo
Red Maple
River Birch
Sycamore
Additional information on rain gardens can be found online at:
Purdue University
https://edustore.purdue.edu/item.asp?Item_Number=FNR-256
University of Wisconsin
https://www.uwsp.edu/cnr-ap/UWEXLakes/Pages/ecology/shoreland/raingardens.aspx
Marion County Soil and Water Conservation District
https://marionswcd.org/water-management/
The Ohio State University Extension
http://hamilton.osu.edu/topics/horticulture/2nd%20Edition%20Storm%20Water%20Manual%20November%202%202009%20PDF.pdf
University of Kentucky Extension
https://water.ca.uky.edu/raingardens