RAIN GARDENS

Creating a rain garden can be as simple as directing rain to an absorbent swale in your yard and putting in a few plants.  If you have no existing place to direct your roof runoff, or if you want a  specifically designed garden, this information will be helpful. Benefits of rain gardens include:
  • Increasing the amount of water that filters into the ground, recharging local and regional aquifers
  • Helping protect communities from flooding and drainage problems
  • Helping protect streams and lakes from pollutants carried by stormwater
  • Enhancing the the beauty of yards and neighborhoods
  • Providing valuable habitat for birds, butterflies and many beneficial insects

Step 1: Determine the best location

  • Where does  gravity take runoff  water ? Go with the flow.
  • Stay at least 10 feet away from the foundation of your house. 
  • Don’t install the garden over any part of a septic system .
  • Check the location of utilities.
  • A sunny or partially shaded location will work best.
  • Don’t worry about mosquitoes breeding in these gardens.  The water soaks away in less time than it takes for insects to mature.

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    Step 2: Check the soils

    Soil types vary in how quickly they will absorb water.  Dig a hole 8 inches wide, 12  inches deep and fill with water.  If it takes more than  an hour for the water to drop an inch, your soil  will need amendment.  Adding sand and compost will help. Soils that have been compacted by heavy construction equipment need to be dug up and loosened to a depth of two feet or replaced with a mix of 50-60% sand, 20-30% topsoil, 20-30% compost.

    Step 3: Determine the size

    Recommendations vary, but a rule of thumb is to multiply square feet of roof area  x soil factor =  area of garden.   Soil factors:  (Sand– .20) (Loam– .40) (Clay - .60). Remember that different parts of your roof may drain to different downspouts.  Estimate only the area that will drain into your rain garden—don’t forget the overhangs.Rain gardens for single-family homes will typically range from 150—400 square feet  (e.g. 15’X 10’ to  20’x20’)

    Step 4:  Design the layout

    The garden should be on a fairly level surface or a berm can be created on the downhill side so runoff can settle in the garden .  A six inch depression near the center  will allow water retention and promote infiltration.  A length of garden hose or rope laid on the ground can help you define the area you want to dig.


    Direct drainage from the roof or downspouts to the garden.  If you must add drainage capacity for compacted or clay soils, gravel or sand or field drainage tile can be installed under the garden site.

    Step 5:  Choose the plants

    This is the fun part.  Native, non-invasive species that do not object to having their roots wet for a few days and are tolerant of dry spells are available. Extensive lists of such plants are available on-line and from Cooperative Extension services.  Examples include Joe Pye, New York fern, buttonbush, New England aster, grasses, etc.  The specific site of your garden will determine which plants you choose.  Remember that the plants near the deeper part of the garden area will have longer periods of wetness. 

    Step 6: Plant, water, mulch and maintain

    The garden will need to be weeded and  mulched for the first couple of years until the plants are large enough to crowd out unwanted vegetation.  Native plants do not require fertilization.  

    For assistance or more information, contact Edith Davey,Ontario County SWCD, 585-396-1450 extension 22.

     
    Some sources of native plant materials are listed here: Native Plant Sources