There's a new garden in town. It is (mostly) easy to install, looks good year-round, requires almost no maintenance and has a terrifically upbeat impact on the environment. No wonder rain gardens are such a great new gardening trend!
Storm water runoff can be a big problem in summer during heavy thunderstorms. As the water rushes across roofs and driveways, it picks up oil and other pollutants. Municipal storm water treatment plants often can’t handle the deluge of water, and in many locations the untreated water ends up in natural waterways. The EPA estimates as much as 70 percent of the pollution in our streams, rivers, and lakes is carried there by storm water! By taking responsibility for the rainwater that falls on your own roof and driveway, you'll be helping to protect our rivers, streams and lakes from stormwater pollution.
To reduce the excess water runoff, many towns are encouraging businesses and homeowners to install rain gardens in their yards. Rain gardens are specially constructed gardens located in low areas of a yard where storm water can collect. The idea is to have the water naturally funnel to this garden. The rain garden collects water runoff and stores and filters it until it can be slowly absorbed by the soil. Rather than rushing off into a storm sewer or a local waterway, the rainwater can collect in a garden where it will be naturally filtered by plants and soil.
You simply dig a shallow depression in your yard and plant it with native grasses and wildflowers; things that are easy to grow and maintain in your area.
What makes a garden a rain garden? First, the garden will be designed with a low spot in the middle to collect and absorb rain water and snow melt. This depression can range from a few inches in a small garden, to an excavated trough that's several feet deep. Second, rain gardens are usually located where they'll catch the runoff from impermeable surfaces like sidewalks and driveways, or from gutters and roof valleys. Third, rain gardens are usually planted with native wildflowers and grasses that will thrive in tough growing conditions. Finally, rain gardens are designed to channel heavy rains to another rain garden or to another part of the garden.
Your rain garden should be located at least 10 feet from the house. The garden’s size and location depends on the yard. The ideal situation would be to locate the garden in a natural depression. You also can funnel water from downspouts on gutters into the garden. The soil should be well drained so the water doesn’t sit in the garden for more than two days. A special “rain garden” soil mix of 50 to 60 percent sand, 20 to 30 percent topsoil, and 20 to 30 percent compost is recommended. You can dig this mixture into the soil to depth of 2 feet before planting.
Once you've identified the new garden's location, remove the sod and dig a shallow depression approximately 6-inches deep. Slope the sides gradually from the outside edge to the deepest area. Use the soil that you remove to build up a slightly raised area on the lowest side of the garden. This berm will help contain the stormwater and allow it to percolate slowly through the rain garden.
If your rain garden is no more than about 6-inches deep, stormwater will usually be absorbed within a one- to seven-day period. Because mosquitoes require seven to 10 days to lay and hatch their eggs, this will help you avoid mosquito problems.
Your downspout or sump pump outlet should be directed toward your rain garden depression. This can be accomplished by a natural slope, by digging a shallow swale, or by piping the runoff directly to the garden through a buried 4" diameter plastic drain tile.
The most difficult part of building a rain garden (if it can even be called that) can be plant selection. Plants need to be tough enough to withstand periodic flooding, yet attractive enough to look good in the garden. Deep-rooted, low-care native plants, such as asters, and tough non-natives, such as daylilies, are best. If properly designed, the rain garden can consist of a blend of attractive shrubs, perennials, trees, and ground covers. Planting strips of grass around the garden and using mulch also can help filter the water.
New plants should be watered every other day for the first two weeks or so. Once they are well established, your garden should thrive without additional watering. Fertilizers will not be necessary, and only minimal weeding will be needed after the first summer of growth.
For more information on creating a rain garden and for sample garden designs, go to: RainGardens.org.