It is not uncommon for areas of the country to experience hot, dry days followed by sudden thunderstorms that drop lots of water in a short amount of time, rather than with long, soaking rains. When a thunderstorm unleashes a torrent of rain, all that water landing on impervious surfaces like roofs, driveways, and walkways often runs off into the nearest storm drain and from there eventually to local waterways, or it goes directly into nearby streams, rivers, and lakes. Even when the rain lands on lawns, gardens, or other vegetated surfaces, so much comes down so quickly in a thunderstorm that much of the needed water runs off rather than soaking into the ground.
The problem with runoff is that it can pick up and carry all sorts of pollutants as it makes its way into the watershed, from nutrients like nitrogen and phosphorous that fuel algal blooms to pesticides, herbicides, oil, grease, heavy metals, and harmful bacteria. Equally important, water that runs off is water that is not available in the soil for thirsty plants to take up. The solution is a rain garden.
A common concern is that a rain garden will become a ″mosquito garden″ as well. But because it's is filled with water for only brief periods of time, you don't need to worry about a rain garden adding to the local skeeter population.
The the leaves of this low-growing summersweet will turn golden in the fall, adding late season color to my rain garden.
I recently installed a rain garden to intercept storm water as it comes off the roof of my house before it sheets across the paved driveway and down the street to the storm sewer. Drainage in my sandy soil is good, so I excavated the area about 6 inches deep; then leveled out the interior and add compost to the soil. I selected both woody and herbaceous plants to provide a changing display of seasonal interest. Most of the plants are natives (or cultivars of natives) of areas of the eastern U.S. and all will weather periods of saturated soil as well as drier conditions. Goatsbeard (Aruncus dioicus 'Kneiffii') begins the floral show in June with arching sprays of ivory-white flowers. Later, spires of fragrant white flowers adorn dwarf summersweet (Clethra alnifolia 'Hummingbird') from midsummer on, attracting butterflies and bees, while purple coneflower (Echinacea purpurea) and turtlehead (Chelone lyonii) add bright notes of color in mid to late summer. Variegated dogwood (Cornus alba 'Elegantissima') provides year-round interest with its green and white variegated leaves in summer, red stems in winter, and white berries that attract birds. Inkberry (Ilex glabra 'Shamrock') with its narrow, glossy evergreen leaves provides a nice textural contrast to the lady ferns (Athyrium felix-femina) that fill in the shadier side of the garden. This new garden is now a lovely spot that will help the environment, wildlife, and the water table -- and add beauty and color to my front yard.
Create your own rain garden and capture the excess water to create benefits all around.