When I first heard the term “rain garden” I thought it was something for people in Seattle. I was wrong. Rain gardens are a way all of us can improve the water quality of our Wisconsin lakes, streams and groundwater.
Rain gardens are just that – gardens that soak up rain water from roofs, driveways and lawns. These gardens increase the amount of water filtering into the ground, which recharges groundwater and reduces the amount of pollutants washing into lakes and streams. And those pollutants are no small amount – the EPA estimates that 35% of surface water pollution comes from runoff from homeowners’ yard care and chemical pollution from household activities. A rain garden soaks up 30% more water than a lawn area of the same size and filters out pollutants in the process.
Think about this is you are on a municipal water supply: why should you let the rainwater that falls onto your property run off into the storm sewer only to purchase it back from the city to water your plants?
Rain gardens are usually placed next to hard surfaces such as sidewalks and driveways or at the end of drain spouts. They can also be located in any low-lying area of the yard. They are designed as shallow depressions three to six inches deep with flat bottoms so that the water spreads out. After an average rainfall, the garden will be wet for about 24 hours. Rain gardens are not designed to handle major downpours so you may want to add an outlet furrow so that excess water drains where you want it to go.
The rain garden should be at least ten feet from your home’s foundation so water doesn’t seep into the basement. Also, avoid locating a rain garden on top of a septic drainfield. There are formulas for determining the proper size of a rain garden for the amount of runoff in a particular area, but the truth is that a rain garden of any size does a lot of good.
Rain gardens are best planted with hardy native plants. They need no pesticides or fertilizers and tolerate the alternating very wet and very dry conditions a rain garden experiences. Some people plant one or more shrubs in the middle surrounded by wildflowers. To keep the garden looking neat, keep the edges tidy with rocks, bricks or some other edging. Tall plants and grasses tend to flop over, so if you want a neat silhouette, stick with short species.
Both the Wisconsin DNR and UW-Extension offices have brochures on rain gardens. Much good information can be found on the internet. Native plants and seeds can be obtained from many native plant nurseries that have sprung up over the past few years.
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