Question: I’ve been hearing a lot about Rainwater Gardens. What exactly is a rainwater garden?
A rainwater garden is garden bed whose purpose is to capture rainfall before it travels very far. It allows the rainwater to soak into the ground instead of washing soil and pollutants into our storm sewers.
The general shape of a rainwater garden is that of a broad, shallow, flat-bottomed basin that is built where rain water tends to flow as it comes off roofs, driveways, sidewalks and lawns. It is not intended to hold water for more than a day, so the soil beneath the garden must be percolation tested to make sure that water will soak in sufficiently.
Rainwater gardens can provide valuable habitat to attract birds and butterflies, while creating beautiful landscaping. Many people prefer to use selected native wild flowers and decorative grasses because they are completely hardy in our climate and they also don’t mind being underwater for short periods of time. Natives can be used in both formal and informal plant arrangements. Natives require very little care and no fertilizing.
The best location for a rainwater garden is where a rainspout, sump pump, or driveway is channeling water in a particular direction. Put on your boots and raincoat and go out during a good rain and watch where the water is flowing. Water coming off lawns and gutterless roofs will also tend to travel in particular directions. Swales between properties also become waterflow areas (and potential gullies). Mark where water is flowing and where it tends to puddle. It often is most effective to place a rainwater garden upslope of where water accumulates, depending on how many directions water is flowing from.
Do not locate a rainwater garden on top of where utility lines are located, atop a septic tank leach field, or over water supply wells. Be careful not to damage tree roots when digging out the garden basin. Do not locate a rainwater garden within 10 feet or immediately upslope of a building that has a basement—remember, the purpose of the rainwater garden is to encourage water to soak into the ground at that point. Farther away from your basement is better. Also, do not put a rainwater garden immediately upslope of a retaining wall unless it was designed with a drainage system.
You can get information and assistance from the various watershed districts in Ramsey County:
Capital Region Watershed District: 651-644-8888
Ramsey-Washington Metro Watershed District; 651-792-7950
Rice Creek Watershed District: 763-398-3070
Maplewood, MN has promoted the installation of hundreds of rainwater gardens. They have a very nice website with lots of pictures of rainwater gardens and further information.
Happy Gardening,
Jennifer Porwit, Ramsey Master Gardener
You may also check out BlueThumb for excellent information on creating rain gardens in our region!
