Raingardens are shallow basins planted with perennials that catch and hold rainwater runoff, allowing it to soak into the ground. This replenishes ground water and helps prevent pollutants from being washed into storm drains and carried to our lakes and streams.
Directing runoff to a raingarden has the added benefit of keeping it away from a foundation. By paying attention to some raingarden basics, the do-it-yourselfer can create this beautiful landscape alternative that offers solutions for water problems in the yard and the environmental benefit of clean water.
Find a good location
Pick a spot that can collect water from an impervious surface such as a roof, driveway or patio. Locating a raingarden near a downspout often makes sense. Keep the garden 10 feet or more from your house to keep water away from your foundation. Also try to avoid disturbing the root systems of mature trees. Do not locate a raingarden above a septic tank or over utility lines, especially gas lines. Get Gopher One Call to mark the utilities before you dig.
Outline the shape of your garden and remove the sod. Dig out the garden like a flat-bottomed bowl with shallow side slopes to the size and depth that suits the plants you selected.Often, a 6-inch depth is all that is needed. Digging the garden any deeper than 6 inches will greatly limit what plants can survive in the garden. Once the basic flat-bottom bowl has been created, add compost and loosen the garden soils to encourage a well-drained garden. Once the soil work is finished, install a 3 inch layer of double shredded hardwood mulch. Do not use chipped mulch. It will float and may end up in the yard or the street.
Have a plan
Plants that like dry conditions go around the edges, while moist tolerant plants go in the center where soils are often much more moist. Consider how wide and how tall plants will get when placing them. Never plant seeds in a raingarden, because seeds float and will never germinate where you have placed them. “Plugs” are an economical alternative to larger plant stock. We suggest a mixture of gallon sized perennials and plugs to save some money but also have some instant gratification from the larger plants you have purchased. Check guides such as Blue Thumb Guide to Raingardens for information on which plants thrive with temporary water inundation as well as other issues such as sun/shade, soil types, and bloom time.
Mulch should be replenished as needed to maintain a 3-inch layer. Water your plants regularly until they are established. Be sure to cut back perennial vegetation before new growth emerges in the spring. This allows birds to utilize the plants for winter food and cover as well as encouraging new growth in the spring. If sand and sediment are washing into the garden from a driveway or road, clean it out. Hint: You can decrease erosion by placing splash rocks where water enters the garden.
Metro Blooms offers Raingarden Workshops in the metro area. Workshops provide in-depth instruction on how to design and install raingardens, effectively use native and other perennial plants, trees and shrubs, employ eco-friendly lawn care practices including minimizing or eliminating fertilizers and the importance of redirecting downspouts. Attendees will receive a packet of support material. The cost to attend the workshop is $10 per household.
“Raingardens are a fantastic solution for preventing stormwater runoff, the number one source of pollution to lakes and rivers in urban areas,” says Michael Keenan, Metro Blooms Lead Landscape Designer. “They are a beautiful and cost-effective solution for protecting our clean water — everyone should have one.”
For more information about rain gardens visit metroblooms.org or call 651-698-1390.