Horticultural expert and gardening consultant Vincent Simeone offers the home gardener detailed and practical ways to create a sustainable home landscape. In Grow More with Less (Cool Springs Press, 2013), Simeone makes the what, how and why of sustainable gardening unmistakably clear. This excerpt, from chapter 5, “Water Conservation,” gives a breakdown on how to plant a rain garden.
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There are several ways to harvest rainwater and maximize the benefits of one of nature’s most valuable resources. Creating a rain garden is one great way. The creation of rain gardens has really started to gain momentum over the last few years, and rain gardens are now common in both commercial and residential sites. This technique is a bit different from harvesting rainwater and collecting it in barrels or cisterns, because rain gardens divert water back to underground water supplies rather than saving it for future irrigation. In fact, rain gardens have much in common with the goals and benefits of permeable pavers. The concept behind rain gardening is quite simple and ingenious; let nature do the work. Rain gardens are low-lying areas that collect rainwater from roofs, walkways, driveways, and other waterproof surfaces. These water collection areas are landscaped with plants that are adapted to regular or occasional flooding. These are typically plants that like “wet feet” but do not like standing water all the time.
The idea of a rain garden is that as this water accumulates and seeps into the ground, the plants, roots, and soil will help filter out impurities in the water before the water makes its way into an aquifer or other groundwater supply. Rain gardens are very beneficial because they reduce storm water runoff and erosion, reduce pollution, and replenish freshwater supplies. When properly installed, they are also very beautiful, lush plantings that can be attractive features in the landscape.
There are some basic requirements you must consider when developing a rain garden for your own landscape. It is not always as simple as selecting a site in your garden that tends to flood during rainstorms and planting some shrubs and perennials in that area. Believe it or not, rain gardens require drainage. Water that stands for too long—several days, for instance—is not a rain garden. It’s a pool of stagnant water. Gardeners should be wary of rainwater collecting and standing for too long, as still water allows mosquitoes and other nasty pests to breed. A properly functioning rain garden should drain rather quickly, certainly within a day. Rain garden sites can be areas that naturally collect water after a rainstorm, or you can help the process along by digging out an area that is convenient for you. Here are a few quick tips to follow when selecting and designing a rain garden.
• Select area of the garden where water naturally flows or collects. Rainwater can be directed to this area by using drainpipes connected to your house’s downspouts. Rain gardens should be placed at least 10 feet from the house and away from the septic system.
• Dig out the area with a shovel to ensure that the subsoil is well drained. If needed, remove heavy soil and replace it with coarse sand or gravel. The sides of the rain garden should be gradually graded toward the middle. Rain gardens are shallow depressions and do not need to be any deeper than 6 to 12 inches.
• On top of the well-drained subsoil layer, spread a 6-inch layer of topsoil for growing plants.
• Before planting, let the area sit for a few weeks. Observe if the soil is collecting water and draining properly.
• Once you are satisfied with the function of your rain garden, plant groupings of ornamental plants that will grow in this low, wet area.
• Plants such as native grasses, ferns, butterfly weed (Asclepias spp.), joe-pye weed (Eupatorium spp.), summersweet clethra (Clethra alnifolia), and winterberry holly (Ilex verticillata) are good examples of plants adapted for this use.
Another factor that you should consider when creating a rain garden is the size needed to accommodate the runoff generated by a given area. A good formula to follow is that a rain garden should be at least one-sixth the size of the area draining into it. If your roof or patio is 20 x 30 feet (600 square feet), you divide that by six to get the proper size for your rain garden. That means that your rain garden needs to be at least 100 square feet or 10 x 10 feet.
If you do not have adequate room for a full-sized rain garden, do not fret. You can create a miniature rain garden by using a big planter or container filled with water-loving plants. Put the container at the base of your downspout, and it will absorb and deflect the water from running all over the garden. If you choose this route, make sure your container is large enough and heavy enough to accommodate dousing. Small, undersized containers will fall over, and plants will become potbound too quickly to serve a long-term function in the garden. Clay, ceramic, or cement pots are excellent materials for a miniature rain garden.
Reprinted with permission from Grow More with Less by Vincent A. Simeone, and published by Cool Springs Press, 2013. Buy this book from our store: Grow More with Less.
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