Robin Trott
Douglas County Extension Service
(320) 762-3890
February 23, 2010
Growing Green
with Extension Educator Robin Trott
Gardening with Water Quality in Mind? Plant a Raingarden!
Does your yard fill with deep ponds during a summer storm? Is your garden plagued with erosion issues? Are you concerned about pollutants running into your lake or stream during heavy rains? Consider planting a raingarden this year. Raingardens are simply saucer shaped gardens that are designed to catch rainwater. They contain wild flower and native plants and are placed to reduce hazardous runoff from roofs, walkways and other impermeable surfaces around your home.
Government studies have shown that up to 70% of the pollution in our streams, rivers and lakes is carried there by stormwater. Raingardens effectively filter this pollution. During stormy weather, runoff collects in the garden, and slowly drains into the ground instead of running into our streams and lakes. Correct placement and construction of a raingarden can decrease storm water runoff by as much as 30%. Raingardens also recharge local and regional aquifers, protect communities from flooding and drainage problems, enhance the beauty of yards and neighborhoods and provide habitat for birds, butterflies and beneficial insects.
If you’re interested in adding a raingarden to your home landscape, consider the following guidelines:
Placement:
Your raingarden should be placed no closer than 10 feet from your house to utilize the roof runoff, or placed further out in the lawn to collect water from your driveway, walkways, lawn and roof. Don’t build your raingarden in an area that is usually wet, as water filtration is slow in wet areas. Build in full or partial sun, but not under trees, and try to choose a site that is on level ground.
Depth:
On level land, raingardens are typically 4-8 inches deep. Gardens deeper than 8 inches tend to retain water too long, those that are less than 4 inches will need to be quite large to accommodate large amounts of storm water. Gardens built on a sloping lawn will vary in depth. (Remember that the bottom of the garden needs to be level.)
Size:
A typical residential raingarden ranges from 100-300 sq ft. Smaller raingardens filter less runoff and have fewer plants, larger raingardens are difficult to make level, and could be very expensive to build and maintain.
Soil:
Determine what type of soil you have. Sandy and silty soils drain rapidly. Clay soils take longer to absorb water, so raingardens in clay soil must be larger than those in sandy or silty soil.
Plant Selection:
Use native plants that bloom at different times to create a long flowering season. Mix heights, shapes, and textures to give the garden depth and dimension. These include but are not limited to native sedges and grasses, marsh marigolds, cardinal flowers, blue bells, bell flowers blue flag iris, anemones, asters, and bulrushes.
For more information about raingardens, try the following websites:
http://www.extension.umn.edu/distribution/horticulture/DG7447.html
http://www.dnr.state.wi.us/ORG/WATER/WM/dsfm/shore/documents/rgmanual.pdf
Remember, by installing a beautiful raingarden, you become part of the team working diligently to keep our native waters clean.
Until Next Time, Happy Gardening!
“Everybody needs beauty as well as bread, places to play in and pray in, where nature may heal and give strength to body and soul.”
~John Muir
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