An Introduction to Rain Gardens: building and maintenancePosted: April 5, 2011
A rain garden is a garden designed to retain rain water, filter pollutants, cut down on the volume of runoff, and help beautify the landscape at the same time. It is suitable for urban environment as it solves problems relating water pollution and excess runoff. Like any other gardening, rain garden does require maintenance and selection of plants. Cities throughout the country have adopted rain gardening to help water management. It is overall very beneficial for an urban environment.
A rain garden, also called bioretention areas, is a shallow depression planted with trees or shrubs, and covered with a mulch layer or ground cover (Clausen and Dietz 2005). This shallow depression contains several benefits:
- Capture, slows down, and encourages water to enter the soil where it can be used by plants.
- Reduces runoff.
- Utilizes rainfall to grow plants and therefore eliminates the need for irrigation.
- Purifies the water by filtering it, reducing the pollution that must be removed before the water can be used again (Kraus and Spafford 2009:15).
The first step of creating a rain garden is finding a good site. The garden should locate at where water ends up after it flows away from the general surface; the place should also have good drainage. Another important note is not to disturb tree roots while creating a rain garden. If you are installing a rain garden around your house, it should be at least ten feet away from the property to prevent wet basement (Ciesinski 2008). Once you find a proper site for installation, you can begin digging for the depression. The depression should be around 4-8 inches deep or deeper depending on how much organic material you want to place on top. Sides should slope gently as straight sides can erode (Ciesinski 2008). An overflow area is strongly suggested as a solution to heavy, frequent rain events. It directs excess water out of the garden without carrying away the mulch and plants. The soil of the rain garden needs to be amended so that water can enter and drain through the soil quickly. Quick filtration of water is critical because standing water induce algae growth and mosquito breeding. The soil is then topped by a layer of mulch or compost, it increases the soil’s ability to absorb and drain water (Kraus and Spafford 2009:24).
The next step is plant selection. Rain garden plants should be able to endure both short periods of flooding and drought. Perennial plants, woody trees and shrubs are recommended (Kraus and Spafford 2009:25). Native plants are also very good plant choices as they adapt to thrive in your soil and climate conditions (Ciesinski 2008).
Rain gardens are relatively easy to maintain. It needs to be weeded from time to time and watered if there is a drought.
Ciesinski, T. 2008. Rain check. Organic gardening 55(6): 62-66.
Kraus, H. and A. Spafford. 2009. Rain gardening in the south: ecologically designed gardens for drought, deluge, and everything in between. Hillsborough, NC: Eno Publishers. 140p.
Dietz, M. and J Clausen. 2005. A field evaluation of rain garden flow and pollutant treatment. Water, air and soil pollution 167(1-4): 123-138.