Rain Gardens – Common Mistakes and Tips

Presented by Denise Sandoval on 4th June 2012

Have a low spot in your yard where water sits for days? Or want to redirect rain water to the land rather than contribute to stormwater runoff?  Diane Sandoval presented a program at the Naperville Community Gardeners meeting.  She is a landscape designer and small business owner of Good-Natured Landscapes LLC, which specializes in native plants and earth friendly landscapes for over 7 years.  She has a horticulture degree, a strong interest in ecology and has been gardening with native plants for many years.  She also works part time for The Conservation Foundation and has been a board member of Wild Ones Greater DuPage for over 10 years.  The following are a summary of her presentation.
Tip: There are no cookie-cutter Rain Gardens

  1. Rain Garden 101: Basics
    1. A shallow bowl or depression, with a level bottom
    2. That captures run-off usually from downspout, sump-pump, sloped area (next to path, driveway)
    3. Depression is planted inside with plants, usually natives to help with infiltration
  2. Tip: Location, location, location
    1. Select an area that is at least 10'or more from your house.
    2. Follow good design that fits with the surrounding landscaping. 
    3. Select an area with sun or part sun and not under big tree roots, utility lines, parkways. 
    4. Call JULIE before digging!
    5. Select an area that gently slopes
  3. Tip: Select an area with good drainage, and avoid a Rain Garden in area where water stands > 24 hours.
    1. Capture /soak-in run-off at highest point. 
    2. Study landscape ( where water flows, collects, drains) 
    3. General Drainage test: make 2 8"x8"x8"  pit in proposed area, fill holes with water, water should drainage < 24 hours.
  4. Tip: Rain Garden Planting Zones 
    1. Inside rain garden on level bottom area = Z1 
    2. Inside rain garden, but at outer sloping edges = Z2
    3. On berm
  5. Choose plants according to amount of sun, moisture & soil texture
    1. Z1, Z2: Drier-moist soils:
      1. Sun, part sun: Nodding Wild Onion, Spiderwort , Culver's Root, Fox Sedge, White Indigo
      2. Part sun, shade: Wild Ginger, Long Beak Sedge , Bellwoft, Woodland Knotweed, Tall Bellflower
    2. Z2: Wetter soils
      1. Sun, part sun: Wild Senna, Blue Flag Iris, Queen of the Prairie, Button Bush, Obedient Plant, Marsh Blazing Star 
      2. Part shade,  shade: Gray's (Morning Star) Sedge, Virginia Blue Bells, Sensitive Fern, Virginia Wild Rye
    3. Z3: Berm: dry-average soil
      1. Create gently sloped mound on down slope or sides to contain water. 
      2. Rule of thumb: Top of the berm should be as high as the top of the upper RG edge 
      3. Think about overflow
  6. Tip: Runoff Entry Ideas
    1. Buried drainage pipe
    2. Gutter downspout
    3. Dry stream bed (gently sloping channel with rocks)
    4. Bioswale (gently sloping channel with plants)
    5. Use rocks, branches to stabilize RG sides, or reduce erosion where run-off enters or where overflow exits
  7. Plan for Overflow
    1. Overflow into surrounding gardens, another rain garden (rain garden chain), or storm drain (soaking up as much as first). 
    2. Bio-swale can take overflow to above areas
    3. Blog article: http://conservationathome.wordpress.com/2012/04/17/where-to-go-with-the-overflow-from-your-rain-garden/
  8. Make shallow (< 4'-6') rain gardens larger in clay soils 
    1. Rain Garden Volume = Length x width x depth (all in feet):
      1. Example 1: Enlarged Rain Garden in clay soils  = 4" deep (4/12' or .333' ), x 10' wide, 6' long = ≈20 cu feet 
      2. Example 2: Rain Garden = 9" deep (9/12 or .75), x 9' wide, 3' long = ≈ 20 cu feet
    2. The longest side of your rain garden should be perpendicular to the flow of water (run-off) & slope.
  9. Tip: Observe rain garden before planting, make corrections 
  10. Final Tip: Check rain garden periodically, especially after a heavy rain, and adjust
  11. Very Final Tip: Educate
    1. Educate your neighbors – tour
    2. Put up a sign
    3. Share your experiences / mistakes / success
  12. Favorite Websites
    1. http://www.raingardens.org/  West Michigan's
    2. http://dnr.wi.gov/runoff/rg/  Wisconsin's DNR
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