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Residential Rain Gardens Graphic: City of Maplewood University of Minnesota Master Gardener Program A rain garden is a water-quality tool that you can use in your own yard. What We’ll Cover What is a “rain garden”? Functions and benefits How to make one Plant selection

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Presentation Transcript
Residential rain gardens l.jpg
Residential Rain Gardens

Graphic: City of Maplewood

University of Minnesota

Master Gardener

Program


Slide2 l.jpg

A rain garden is a

water-quality tool

that you can use

in your own yard.


What we ll cover l.jpg
What We’ll Cover

  • What is a “rain garden”?

  • Functions and benefits

  • How to make one

  • Plant selection

  • Maintenance

  • Cost

  • Helpful resources


What is a rain garden l.jpg
What is a “rain garden”?

  • A shallow sunken garden that recycles the rain

    • less than 8” deep

  • Rainwater runoff is directed toward it

  • Runoff soaks in

Photo: Mary Nolte, Fulton neighborhood, Minneapolis


Plants help recycle the rain l.jpg
Plants help recycle the rain

  • Plant roots absorb water

  • Water goes up the stem

  • Leaf surfaces release moisture

  • Water returns to the atmosphere as a vapor


A rain garden is also known as l.jpg
A rain garden is also known as ...

  • Mini wetland

  • Water quality garden

  • Stormwater marsh

  • Planted swale

  • Bio-retention pond

  • Strategically placed puddle


Functions of a rain garden l.jpg
Functions of a Rain Garden

  • Diverts runoff from paved surfaces

    • Driveways, roofs, streets, patios, walks

      • Water moves “sideways” – runs off pavement

  • Keeps runoff on site

    • Instead of flowing untreated into streams and storm sewers

  • Soil acts like a living sponge

    • Water moves “down” - into the ground


Benefits of a rain garden l.jpg
Benefits of a Rain Garden

  • Soaks up 30% more runoff than lawns

  • Filters polluted runoff

    • sediments, fertilizers, pesticides

  • Recharges groundwater

  • Helps prevent flooding

  • Provides habitat/food for butterflies, birds

  • Beautifies a low spot in the yard


Polluted runoff harms water quality l.jpg
Polluted runoff harms water quality

  • Flows into waterways untreated

  • Harms fish and wildlife

  • Kills vegetation

  • Fouls drinking water supplies

  • Makes recreation areas unsafe


Every curb is a shoreline l.jpg
Every curb is a shoreline

Grass clippings and leaves are the main source of phosphorus in lakes and streams

Rain gardens act as filters and remove:

  • 94% of sediment

  • 43% of phosphorus

  • 70% of nitrogen


Design features are flexible l.jpg
Design Features are Flexible

Variables include:

  • Location

  • Soil

  • Size and shape

  • Plants


Location of the rain garden l.jpg
Location of the rain garden

© Fitch & Co.

www.montgomerycountymd.gov/mc/services/dep/greenman/rain.htm


Go with the flow l.jpg
Go with the flow

  • Observe the drainage pattern in your yard

  • Locate the garden:

    • in a natural low spot

    • near sidewalks, driveways, or other paved surfaces

    • down-slope from roofs, gutters, downspouts, sump pump outlet

  • Direct water into rain garden

    • channel or buried plastic pipe




Bird s eye view of rain garden locations l.jpg
Bird’s-eye view of rain garden locations gentle slope

Graphic: UW Extension Service


Traditional path of roof runoff l.jpg
Traditional path of roof runoff gentle slope

Graphic: Applied Ecological Services, Inc.


Average runoff from a roof is 24 000 gallons per year l.jpg
Average runoff from a roof gentle slope is 24,000 gallons per year

That would fill 600 bathtubs!



Rain gardens in home landscapes l.jpg
Rain Gardens in gentle slope Home Landscapes

In a back yard catching runoff from the garage

In a front yard catching runoff from a downspout


The soil must drain l.jpg
The soil must drain! gentle slope

  • A rain garden is NOT a pond.

  • Percolation test:

    • fill a 6-inch-deep hole with water

    • should drain within 24 hours

    • if not, don’t put a rain garden there

    • or amend soil

  • “Rain garden soil mix”

    • 50-60% sand, 20-30% topsoil, 20-30a% compost


How big l.jpg
How big? gentle slope

  • No standard size

  • Rule of thumb: 1/3 of drainage area

    • e.g., 170 sq. ft. (10’ x 17’) garden for 500 sq. ft. of drainage area

  • Factors include slope, soil type, distance from runoff point

  • Even a small rain garden is beneficial


Calculating drainage area l.jpg

Length of house 100 feet gentle slope

Width of house 20 feet

L X W = 2000 sq ft

2000 sq ft ÷ 4 = 500 sq ft draining to the rain garden

Area of roof going

to down spout

Calculating Drainage Area

Length

Width

Graphic: UW Extension Service


Designing the rain garden l.jpg
Designing the rain garden gentle slope

  • Call Gopher State One: 800-252-1166

  • Outline it with rope or hose

    • curvy shape

  • Remove sod and dig to desired depth


  • Designing the rain garden cont d l.jpg
    Designing the rain garden – cont’d gentle slope

    Features:

    • gently sloping sides

    • flat in the deepest spot

    • berm at low end

    • grass filter strip on top edge

    • mulch – shredded bark


    A soil berm acts like a bumper keeps water from flowing over edge l.jpg
    A soil berm acts like a bumper – keeps water from flowing over edge

    Berm

    Photo: UW Extension Publication GWQ037


    Slide27 l.jpg

    Rain Garden Collects Parking Lot Runoff over edge

    Photos & design: Kestrel Design Group

    Spray paint outlines the garden shape


    Slide28 l.jpg

    Parking lot runoff flows into the over edgerain garden instead of into the street

    Runoff pools in the garden, then seeps into the ground

    Photo nd Project by Kestrel Design Group


    Bird s eye view of a rain garden l.jpg
    Bird’s-eye view of a rain garden over edge

    Graphic: UW Extension Publication GWQ037


    Layout for a 140 sq ft garden l.jpg
    Layout for a 140-sq.ft.-garden over edge

    Graphic: UW Extension Publication GWQ037


    Slide31 l.jpg

    Before over edge

    Buried pipe connects to downspout

    Berm

    Photos: Mary Nolte

    After



    Select perennial plants that l.jpg
    Select perennial plants that over edge

    • Tolerate both wet and dry spells

      • plants that like wet feet in deepest part

        • e.g.: Blue flag iris, marsh milkweed, big bluestem, sedges, red-twigged dogwood, buttonbush

    • Tolerate de-icing salts (if near roads)

    • Match up with soil and light conditions


    Native plants have advantages l.jpg
    Native plants have advantages over edge

    • Adapted to the climate and native pests

    • Deep rooted

      • long roots make channels in the soil for water to follow

    • Havens for butterflies, birds, beneficials


    Prairie plants have deep roots l.jpg
    Prairie plants have deep roots over edge

    Graphic: Conservation Design Forum Inc.


    Rain gardens in maplewood mn instead of curbs and gutters l.jpg
    Rain gardens in Maplewood, MN over edgeinstead of curbs and gutters

    Photo: City of Maplewood


    Sun gardens l.jpg
    Sun gardens over edge

    Photos: City of Maplewood


    Garden for light shade l.jpg
    Garden for light shade over edge

    Photo: City of Maplewood


    An easy shrub garden l.jpg
    An easy shrub garden over edge

    Shrubs:

    • Annabelle Hydrangea

    • American Highbush Cranberry

    • Anthony Waterer Spirea

      Perennials:

    • Marsh Milkweed

    • Stello d’Oro Daylily

    Photo: City of Maplewood


    Maintenance l.jpg
    Maintenance over edge

    • Pull weeds (esp. the 1st year)

    • Water ~3 x a week until established

      • also during a dry spells

    • Mulch

      • shredded hardwood won’t float away

    • Cut back or mow down


    What about mosquitoes l.jpg
    What about mosquitoes? over edge

    • A rain garden is not a pond

    • No standing water between rainfalls

    • Mosquitoes need at least 7 days in standing water to hatch

      • will not survive if wetland dries out in less than a week.


    Estimated cost and plants needed l.jpg
    Estimated cost and plants needed over edge

    • Do-it-yourselfers:

      • about $3 to $5/sq. ft.

    • Professionals:

      • about $10 - $12/sq.ft

    • Plants needed for 300 sq. ft. garden

      • 100 for wet zones

      • 200 for upland zones


    Summary l.jpg
    Summary over edge

    • Shallow saucer shape

    • Strategic location

    • Plants match soil and moisture levels

    • Soil drains

    • Size appropriate for yard and drainage area

    Photo: Mary Nolte


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