Typical turfgrass lawns that are installed in every neighborhood absorb small amounts of water during rain events and can be costly to maintain. They require the application of fertilizers and pesticides to keep them green and weed free, and do little to regenerate the water table or promote natural cleansing of the storm water that falls on them.
While some of the rain that falls on our typical turfgrass lawns is absorbed, most of the rain water cannot be absorbed because the root system is very shallow – only 4-6” deep; this is called “run off”. When a turfgrass lawn becomes saturated during a rain event, the excess water, chemicals, and fertilizers used to treat the lawn run offsite and end up downstream in nearby Schaumburg neighborhoods and neighboring communities.
Farm fields that in the past only flooded occasionally in the early spring, now flood every year and with every rain. Homeowners across the USA are catching on to rain gardens; slightly depressed landscaped areas that are planted with native grasses and wildflowers. These garden areas soak up rain water from the roof or sump pump of a house and also the runoff from paved areas such as parking lots, sidewalks, and streets. Rain gardens are an infiltration technique – water is captured in a garden that features native plantings, slowly filtering into the ground rather than running off into the storm sewer. Rain gardens are a way for homeowners as well as businesses to participate in the reduction of polluted runoff by allowing about 30% more water to soak into the ground than a conventional lawn.
One rain garden can seem small, but collectively they produce substantial community and environmental benefits. Rain Gardens make good use of rain water runoff and conserve precious water supplies, protecting the water quality of downstream rivers and lakes. Rain gardens use little or no fertilizer and pesticides, and need minimal maintenance once established. While native grasses and wildflowers are beautiful to look at, they are also very hard working. The roots of native wildflowers and prairie grasses typically go twice as deep into the ground as they are tall, thereby absorbing much more water and pollutants. And there’s more - rain gardens attract birds, butterflies, beneficial insects such as dragonflies, which eat mosquitoes!
Rain gardens will enhance the beauty of your neighborhood in summer, but also in winter when the seed heads can be an appreciated food source for our winter songbirds. They can be a great project that can be used to teach our children about protecting the environment and enjoying nature’s beauty at the same time. And, science shows that they do not attract mosquitoes if built properly.
Rain gardens are well situated near a downspout or at the point of your sump pump discharge in full sun or partial shade. Place your garden so that the pipes from the downspout or sump pump can drain directly into the rain garden; about 10 feet away from the foundation and down slope from the building. You can dig a shallow swale for the water to run into the rain garden, or pipe the runoff through a buried 4” black plastic drain tile that will empty into the rain garden. If the pipe from your sump pump pops up into your lawn, place a screen mesh over the pipe to make sure small animals don’t take up residence in the pipe and to keep wood chips and plant debris from clogging the pipe.
If your rain garden is situated to absorb the water from your sump pump, take care in placing your garden correctly so that the discharge line extends at least 3’, but no more than 10’ from the exterior wall of your house.
Before digging anywhere, call J.U.L.I.E. at 800-892-0123 to have the underground utilities located in your yard. You don’t want to accidentally cut your cable TV., telephone line, or any other buried utility.
Rain gardens should be kept out of the parkway which is the area typically between the sidewalk and the street, and from drainage swales where the garden could obstruct the flow of rain water to the storm sewer or adjacent drainage swales.
Rain gardens are sunken gardens approximately 4-6 inches deep with a flat bottom. They should be approximately 1/3 the size of the area that is draining into it – usually a roof, yard, or driveway. They can be any shape, and can be natural or formal looking depending on the plants selected and the desire of the homeowner.
Care must be taken to make sure that the garden will be sufficiently sized for the amount of water it needs to soak up. One way to approach a smaller rain garden is to dig up a small area near your downspout and observe it during a downpour. If there is no overflow and all of the water infiltrates quickly (within 2 or 3 hours) after the rain stops, it is okay to go ahead and plant it in that location.
The soil in the rain garden should be modified to have higher infiltration rates and so it won’t compact like clay. A quick rule of thumb is to mix 1/3 sand, 1/3 topsoil, and 1/3 compost into the bottom of the garden area.
Any size rain garden, even a small one, makes a difference. Start by making a difference in your yard; you’ll have an impact on your neighborhood, your watershed, local streams and lakes, and everybody that is downstream from you – all this with just one garden!
For more information about rain gardens contact Martha Dooley, Landscape and Sustainability Planner, at 847.923.3855.