We have a large parking lot and paved area here, and every time it rains the water comes this way because of the slope of the parking lot. This area used to be a low area that held water anyway.
The area was dug out and lowered slightly, and plants were added that have deep roots and can absorb a lot of the water. Now the water comes in and it’s absorbed by these plants and filtered by the soil. It doesn’t reach the street anymore.
You want the water to drain within twenty-four hours. We don’t want to create a mosquito breeding ground. Typically rain gardens are six to twelve inches deep, so they don’t hold water for a long period of time.
There are a lot of native plants that do well in a rain garden. Coneflowers are recommended. We have a plant called Allegheny Monkey flower. It does really well in here. We also have some plants that aren’t native, but they’re well adapted to the area. For instance, we have day lilies, blue flag iris, cleome, and viburnums. The most important thing when you’re selecting plants for a rain garden is to choose plants that can handle wet and dry, because rain gardens aren’t wet all the time.
A good way to build an entrance to a rain garden is to use an inlet with lots of rocks. That’s what we’ve done here. This will collect the runoff from the parking lot, and it also breaks that stream of water to keep the soil from washing out of the garden later.
We’ve chosen to use the native grasses in the back end of the rain garden. So, if water is flowing across the grasses, it slows down the water and breaks up the stream. They also have deep roots to soak up a lot of that water.
The garden is bowl-shaped. On the back end, it comes up like the back edge of a bowl. We’ve placed some rocks there, so that if the water does spill over the back, those rocks break up the flow and then it’s dispersed evenly across the grass behind that area.
This feature story prepared with Jennifer Smith, Kansas State University Research and Extension Horticulture Agent, Douglas County. For more information, visit your local county extension office or visit our website at KansasGreenYards.org.