A Rain Garden
A rain garden is a planting area that captures runoff from rain that falls on roofs, driveways or yards. They help create landscapes that are both beautiful and hydrologically functional. These types of landscapes hold and infiltrate water, rather than generating runoff that causes water quality problems and contributes to flooding.
It is a depression or shallow bowl made in the landscape that is level from side to side and end to end.
Runoff that travels to your rain garden is temporarily ponded (the water does not stay long).
The captured runoff in a rain garden allows water to infiltrate into the soil, rather than running into streets and storm drains.
Relies on soils with good percolation rates (clay, not so good).
Location is critical. It must be located so runoff goes towards it. Look for low spots, but soils must have good percolation rates. Water should not stand in an area for more than twelve hours.
Rain gardens should not be located upslope from a house or closer than ten feet from a foundation.
Native plants are recommended for rain gardens. These will develop deep root systems that generate high organic matter and porosity, plus the right choices can tolerate temporary flooding and extended periods of dry weather. These also don't need fertilizer...in fact, it's important that you do not fertilize.
I've gently borrowed all this wonderful information from the Iowa Rain Garden Design and Installation Manual. I encourage you to take a peek at this resource for more detailed information on plant choices (for zone 5), soil percolation rates, plus how to install and size a rain garden.
I've also created a Rain Garden Pinterest board to show you more wonderful examples.
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