With all of the recent rains, we have had to modify our rooftop drainage and I decided to investigate rain gardens. One of the articles asked these questions. Do you worry about pollutants such as fertilizer and pesticides going into our lakes and rivers? Do heavy rains collect in areas of your yard?
Air pollution from cars, trucks and factories is gathered in rainwater as it falls. As the water rushes to the storm sewers, it gathers all sorts of debris from streets and lawns. Storm water runoff is the greatest pollutant to waterways. The easiest way to help water infiltrate into the ground rather than run off into the storm sewers is by creating a rain garden.
Rain gardens are vegetated depressions that collect rainwater run-off and the pollutants it carries from rooftops and paved areas. Rain gardens slow down and cleanse the storm water and in doing so reduce erosions, contamination and algae growth in rivers and lakes. Water is captured in a basin shaped garden filled with mainly native plants.
The first step in creating the garden is to identify the surfaces from which the water runs off, including lawns, sidewalks and driveways. Assess the direction of the water flow and locate natural wet spots. Keep in mind that an area that always has standing water is not a rain garden - it is a pond, water garden or wet land. Rain gardens experience both saturation and dry soil conditions.
Getting started may be as easy as capturing water from eaves troughs in a container or making a garden at the end of a downspout. Other locations may be near the sidewalk, driveway or street, but they must be at least ten feet away from building foundations. It is possible to use an existing garden.
Plan your location and size. A typical residential garden is 100 to 300 square feet and from six inches to 12 inches deep. Do not go deeper in clay soil or the water will tend to pond. Before you start to dig use the 'one call' number to check for underground utility lines. Use stakes and string to check the elevation and a rope or hose to outline the shape. Remove the sod and till the soil. Aim to create a concave depression with the bottom perfectly flat so the water will distribute evenly. If your soil is permeable, mix in compost, but if it is not replace it with a mixture of 60 percent sand, 20 percent compost and 20 percent topsoil. Add a thick layer of mulch over the top. Some gardeners choose to surround the bed with plastic or decorative edging.
You can plant the garden in a naturalized or formal look and it can be in a sunny or shady area. Plant deep-rooted shrubs and perennials that can tolerate drenching, drought and your soil and light conditions. Do not use wetland plants that need to be in standing water. Native plants are highly recommended for at least 50 percent of the vegetation, but some cultivars (cultivated varieties) work well too. It is a good idea to use half grasses (sedges) and half flowers.
Native plants are colorful and beautiful and have adjusted to our long winters and varying water flows. They have long and thick root systems (up to 16 inches) suited to drawing water deep into the underground. They leave empty channels along last years roots that gives moisture 'pipes' to re-enter the ground. They require little maintenance and no fertilizer or pesticides. Some plants with very deep roots include sun lovers Coneflower, Liatris and Rudbeckia. Astilbe and Sedges are moisture lovers for shady areas.
The garden will tend to have three areas with the center area the wettest, next to a moist area and a dry area around the edges. Site the plants according to their individual needs. Pull the mulch aside to plant them, water them in well and keep them weeded until they are established.
If properly constructed the garden will drain the water within two days. It will remove pollutants and excess nutrients and attract wildlife. Through interception, infiltration and evaporation it will recharge the ground water for drinking and slow the rate and volume of water to the waterways. If that is not enough, it can be beautiful and enhance your landscape.