Fanatical Botanical: Rain gardens help manage water runoff - Storm Water Jobs

Fanatical Botanical: Rain gardens help manage water runoff


RAIN GARDENS -- Weather in the fall and early winter can be quite unpredictable. A great example was this past week, when temperatures in the 60s on Sunday gave way to a threat of snow later in the week. Sometimes, swings in weather patterns can cause problems in the landscape. One issue is water runoff, which can cause ponding during an unexpected rain downpour. There is, however, a creative solution to this problem: the aptly named rain garden. Rain gardens work to trap and filter large amounts of water while also encouraging evaporation. The gardens can prevent water from running off into streets, effectively helping urban areas in stormwater management. In fact, the City of Roanoke offers a credit toward a homeowner’s stormwater utility fee if a rain garden has been installed. Many rain gardens are found at the bottom of ravines and hills. Some are built from scratch by homeowners, and some have been worked into new construction. A beautiful new rain garden has been installed at the Williamson Road branch library in Roanoke, which reopened in November after renovations. According to a Virginia Cooperative Extension online guide, a rain garden should include “plants and soil that specifically clean pollutants from fallen rain water.” Native, noninvasive species are preferred, and the garden should include a variety of plant heights. Before choosing plants, it’s important to plan your rain garden’s layout. A garden should be built in a depression, or a well-constructed hole. Determine the areas that will be the driest (at the top of the depression) and the wettest (in the bottom). The VCE guide refers to these areas as moisture zones. Choose plants for your garden that can take both extreme drought and extreme flooding at different times. Plants that prefer “wet feet” should go in the bottom of the depression, whereas plants that have strong roots and can take drought conditions should be further up the sides of the hole. According to the VCE guide, for every 10 to 20 square feet of planting space, a new species should be introduced. Below, I have prepared a short list to get you started on your rain garden plans. For more suggestions on plants to use, as well as garden layout and maintenance tips, visit and search for “rain garden plants.” Trees According to the Virginia Cooperative Extension, trees should only be used in rain gardens larger than 150 square feet. Small tree options include downy serviceberry, dogwood and redbud. For the most part, trees that work best in rain gardens are larger. These include cryptomeria, dawn redwood (my all-time favorite tree), bald cypress and the ever-popular river birch.

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