Rain gardens help control stormwater runoff and attract wildlife
June 26, 2015 Release for Tallahassee Democrat
By Geoffrey Brown
Isn’t Wakulla Springs BEAUTIFUL!? If you’ve been there, I am sure you’d agree that it is a local gem worth conserving for future generations. Reflecting on all the rain we’ve received this past winter and early spring, it’s important to remember the collective impactimpervious surfaces have on water quality in the Springs as well as other water bodies downstream. Due to continued development in our community, increasing stormwater runoff is decreasing the quality of our water by hampering its natural filtration on its journey down into the ground through to the aquifer.
Managing stormwater runoff is one of the nine important “Florida-Friendly” yard management practices included in the Florida Yards and Neighborhoods program to encourage us all to be good environmental stewards. There are a number of ways we can slow down the runoff around our homes and businesses to promote percolation of stormwater, thereby allowing better physical filtration and biological processing to occur. Building a rain garden is one of these ways. It takes some planning, however rain gardens are a very proactive way to reduce run-off by corralling it from your downspout, patio, driveway or any other non-pervious surface before it has the chance to leave your yard. Rain gardens are also an opportunity to attract wildlife to your yard—another Florida Friendly Yard management practice!
Rain gardens are slight depressions constructed in the landscape that hold water which would otherwise contribute to stormwater runoff. Rain gardens resemble a swale that has been enclosed by a berm built on the downhill slope. They allow stormwater to percolate slowly, so that pollutants in the water are processed biologically and filtered physically through the soil. A variety of plants are used to landscape rain gardens so that not only are they functional, but they contribute to the beauty of your landscape as well. What makes rain gardens so interesting to gardeners is the selection of plants which thrive in (or are tolerant of) conditions of both flooding and times of drought.
Let’s first talk about rain garden placement. For selecting a site, choose a relatively sunny area that receives a lot of water already. A common area for many homes or businesses is the area that collects rainwater not far from the base of a rainspout, or runoff from the roof. The best areas are far enough away from the base of trees to minimize digging around roots. The size of the rain garden is proportional to the size of the roof or amount of water the area receives during rain events. Sometimes runoff from new development may create flooding where there was none before. Rather than removing the water off the slope, a rain garden holds water to slowly let it percolate into the soil. In cases of yards with predominant clay, some soil amendments such as sand and gravel may be needed to enhance percolation.
Once you’ve determined the size of the rain garden, the site needs to be prepared. The finished garden should be roughly about eight to ten inches deep. Soil dug from the inside of the depression is used to build up a berm on the downhill slope of the rain garden. The bottom of the rain garden should be level, to promote percolation evenly. The amount of work required for building the rain garden depends on the type of soil, slope and final size desired (and the presence of roots!) A fairly detailed step-by-step manual for constructing a rain garden is available at TAPPWATER.org. Contact the TAPP Coordinator Courtney Schoen at Courtney.Schoen@talgov.com or directly at 850-891-8754 for additional advice, as well as the UF/Leon County Extension Office. Grant money is available to defray the cost of some supplies and plants.
Contribute to the beauty of your rain garden landscape with well-placed lime rock or logs, which will additionally provide visually-pleasing areas for reptiles or amphibians to lounge. The addition of a well-maintained birdbath will draw in songbirds, especially during dryer times. Plan the location of your rain garden oasis accordingly so you can watch the wildlife gather from an indoor window, back porch or patio.
Here is a short list of plant possibilities to consider, based on amount of sun at the site.
Shrubs or small trees
Beautyberry- Callicarpa americana
Saw palmetto – Serenoa repens
Florida azalea – Rhododendron austrinum
Buttonbush- Cephalanthas occidentalis
American Snowbell – Styrax americanus
Virginia sweetspire – Itea virginica
Yaupon holly – Ilex vomitoria
Walter’s viburnum – Viburnum obovatum
Oakleaf hydrangea – Hydrangea quercifolia
Swamp sunflower- Helianthus angustifolius
Swamp rose mallow – Hibiscus grandiflorus
Perennial plants and grasses
Wild white-indigo – Baptisia alba
Black-eyed Susan – Rudbeckia hirta
Cone flower- Echinacea purpurea
Blue-flag iris – Iris virginica
Canna lily – Canna spp.
Cinnamon fern – Osmunda cinnamomea
Royal fern – Osmunda regalis
Blue-eyed grass – Sisyrinchium angustifolium
Muhly Grass – Muhlenbergia capillaris
Fakahatchee grass – Tripsacum dactyloides
Coontie – Zamia floridana
Rain Lily – Zephyranthes spp.
Find out more information about constructing rain gardens and plant lists at the following sites:
Florida Yards and Neighborhoods nine concepts: www.floridayards.org/landscape/tutorial.php
Tips for constructing rain gardens, grants and technical advice: www.tappwater.org/rain-gardens
Plant choices: www.floridayards.org/fyplants/plantquery.php
Geoffrey Brown is a lab coordinator in the Department of Biological Science at Florida State University and a volunteer writer for the Leon County UF/IFAS Extension. For gardening questions, email us at Ask-A-Mastergardener@leoncountyfl.gov