Next time it rains, head outside and take a look at the route stormwater runoff takes onto and through your property. Does the water come off the street, driveways, your roof, downspouts? Does it go directly into a storm drain, an open drainage ditch, the neighbor’s yard? Maybe it sheets across your lawn or cuts channels down your slopes. If it comes to rest in a low-lying area, leaving you with an unwanted “pond” and a soggy landscape, your yard could be a good candidate for a rain garden!
What are rain gardens?
Rain gardens are shallow depressions planted with deep-rooted native plants and grasses that are especially effective for residential use. Even very small areas can absorb as much as 30 to 40% more runoff than a standard lawn. While rain gardens won’t solve all stormwater runoff and erosion problems, they serve many beneficial purposes when properly constructed and positioned.
Why have a rain garden?
The primary reasons for rain gardens are diverting water away from your house and handling standing water in the landscape. When well-designed, a rain garden creates a lovely, interesting focal point in your garden!
Important environmental reasons to embrace rain gardens include:
- Minimizing runoff into storm drains and creeks
- Filtering pollutants and sediment carried in stormwater runoff through rain garden plants, mulch, and soil
- Gradually soaking rainwater into the ground
- Nourishing plant life and replenishing groundwater tables
- Providing habitat for wildlife, butterflies, and beneficial insects
Will my rain garden become a pond?
The short answer is “no,” although several types of stormwater management systems are called “retention ponds.” These include wet ponds, dry ponds, and rain gardens:
- Wet ponds are constructed basins on large drainage sites that have permanent pools of water, at least through the wet season. They are complex ecosystems that hold and treat rainwater before it flows downstream.
- Dry ponds—usually constructed of concrete or rock beds—immediately remove concentrations of rainwater from an area.
- Rain gardens slow down stormwater runoff and hold it for a short period of time—no more than 24 to 48 hours. Water collected in a rain garden usually seeps into the ground within an hour or two. Therefore, a rain garden should not contain any permanent pools of water.
A word about mosquitoes. They won’t find rain gardens to be good breeding areas. It takes mosquitos 10 to 14 days to go from egg to adult, and any water standing in the rain garden is long gone before then!
Things to think about
Multiple factors inform the way you design your rain garden—its depth, width, lining, layers of materials, and types of soil. Factors to consider when planning a rain garden include:
- Soil composition
- Volume of water
- Space available
- Distance from the house
- Amount of sun and shade
You’ll also have to decide what plants to use. A combination of trees, shrubs, grasses, and flowering perennials will produce the most aesthetic appeal, but some plants may need to handle both wet and dry conditions. Others may need to tolerate different levels of water—both amount or volume—and force or velocity.
The winter months are a good time to plan and get started constructing your rain garden. To learn how, watch for these blogs over the next several days: building a rain garden, planting a rain garden, and maintaining a rain garden.
Backyard Rain Garden
by NC Cooperative Extension, 2015
Rain Gardens: Green Solutions to Stormwater Pollution
by Clemson University, South Carolina, Feb. 2009
Provides A to Z information with good diagrams. Be sure to adapt plant and soil recommendations to N.C. Mountains.
Article written by Beth Leonard, Extension Master GardenerSM Volunteer.