How to Build a Rain Garden

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How to Build a Rain Garden

• Produced by University of Wisconsin Extension
• Wisconsin Department of Natural Resources

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Deciding on the best spot to site your rain
garden

• Integrate with your existinglandscaping

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Captures both porch rain water and spring sump
pump At least ten feet from a foundation
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Wheres the Best Place?

• How about where water ponds
• Depends
• Wetland soil?
• Sealed bottom?
• Groundwater?
• Uphill, to catch and infiltrate water

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Deciding on the best spot to site your rain
garden

• Do not locate over or adjacent to your septic
  system
• Long roots can interfere with system,
• Dont want to add more water to the system, which
  is sized to infiltrate water from the household.

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Slope Important Flat Bottom helps Spread out
the Water
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Backyard Rain Garden 300 sq. ft. Madison, WI
Roof Area 1000 square feet
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How to Size a Rain Garden
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Questions to ask yourself What type of soil
do I have? How big is the area draining to the
rain garden? What is the best size to fit my
yard?
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Calculating Drainage Area

• Area of roof going
• to down spout

• Length of roof 30 feet
• Width of roof 15 feet
• L x W 30 x 15 450 sq ft

Length
Width
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Determining Size of Drainage

• Rain Gardens, away from house, can be smaller
  lawn infiltrates some of the water.
• Need to check yard runoff (neighbors too)

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Determining Your Soil Type

• Some hints
• Soil feels gritty and coarse sandy
• Infiltration Rate of Sandy Soils 2.5 in/hr
• Soil feels smooth not sticky silty
• Infiltration Rate of Silty Soils 0.5 in/hr
• Soil feels sticky and clumpy clayey
• Infiltration Rate of Clayey Soils 0.3 in/hr
• Have soil analyzed
• Use perc test

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Using Size Factor and Depth to Determine Final
Rain Garden Size with 100 Control
Less than 30 feet from downspout
More than 30 feet from downspout
Example 1 450 sq ft x .25 112 sq ft rain garden
Example 2 450 sq ft x .43 195 sq ft rain garden
Example 3 450 Sq ft x .10 (30 feet) 43 sq ft
rain garden
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Rain Garden Depth Size

• Balance between
• drainage area
• slope
• soil
• desired garden size

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Picking the Plants

• Decide on formal or informal look
• Choose plants for conditions sunny shady
• Choose plants for year-round interest

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Plants to Look Out For

• Look a-likes
• Beggar ticks
• Goldenrods
• Some Grasses

Re-seeders Most asters boltonia
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Time to get to work a family affair!
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From Start to Finish

• Jefferson County UWEX OfficeRain Garden

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Oops!
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Add a weed barrier and mulch
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Turf Rain Garden 50 Sq. Ft.
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Cost of Rain Gardens

• If you do the work but purchase plants,cost
  is about 2 to 5 per square foot. Plus costs
  for mulch, soil amendments
• Cost of landscape consultants in Wisconsin is
  about 15 -25 per square foot.Includes design,
  construction, plants, mulch and planting. More
  for woody shrubs or trees, stone or if complex
  conditions
• Therefore a 100 square foot rain garden
  costsbetween 200 and 2,500.

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Remember These Steps

• Determine size and location
• Design shape and select plants
• Talk to neighbors
• Call diggers hotline 811 or800-242-8511 before
  you dig!

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Answering Neighbors Concerns

• Mosquitoes?
• Rain gardens drain in five days.
• Mosquitoes 7 to 12 day life cycle
• Disease carrying mosquitoes dont live in ponds.
  They prefer small amounts of standing water such
  as holes in trees, old tires or bird baths.

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Other lessons learned

• Small immature plants, cant handle flooding or
  drought.
• Keep tags by plants to help with weeding
  especially first couple of years.
• During extreme or frequent rains, check to see if
  draining, if not, temporarily breech berm.
• During droughts, watch to see if watering needed.
  
• Dont applying herbicides uphill!

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Long Term Maintenance
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Other Things to Consider

• Weed ordinances
• Check the web, most communities have them under
  nuisances
• Ok if they use DNR noxious weed list
• Sample language for modifying weed ordinances at
  Wild Ones http//www.for-wild.org/weedlaws/weedla
  w.html
• Downspout disconnect ordinances

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Thank You!
For more information http//clean-water.uwex.edu
/pubs Produced by Suzanne Wade, Jennifer
Erickson University of Wisconsin-Extension Kri
sti Minahan, Roger Bannerman Department of
Natural Resources Photo Credits Roger
Bannerman, Jim Bertolacini, Margaret Burlingham,
Center for Watershed Protection, DNR and UWEX
file photos, Matt Hanson, Carolyn Johnson,
Maplewood MN Public Works, Bob Queen, Ellen
Rulseh, Bill Volkert, Suzanne Wade, Larry Coffman