Rain Garden Design Rain Garden Process Maintenance Construction
Typical Situations Site Analysis Site Inventory Soil Amendments

How to Design a Rain Garden

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Rain gardens, step by step.  What to do after you decide you want to have a rain garden but don’t know where it should go or what it could look like.

| Site Inventory | Site Analysis | Garden Design Concept Development |
| Garden Design &/or Choose a Garden Template | Plant Lists |
| Garden Installation & Care


    1. Inventory the site (Site Inventory)
    2. Analyze the site (Site Analysis)
    3. Find the design inspiration for the project (Concept Development)
    4. Design a garden &/or choose a template (Design)
    a. Mesh the analysis with the design idea (concept) and organize circulation and desired use functional areas
b. Critique idea / check to see if your design ideas are met by design solution; adjust as necessary
c. Create a map of what you will plant based on your site and design ideas
d. Create a list of plants to buy (Plant schedule) and plants to move/reinstall
e. Determine what soil amendments and/or pipe you need
    5. Prepare area (Site Preparation)
    a. Layout the plan on the ground
b. Excavate and install underdrainage if you are providing underdrains
c. Add appropriate soil amendments
d. Edge bed as desired
    6. Purchase plants and mulch
    7. Layout plants according to the plan; adjust as necessary
    8. Install plants
    9. Apply mulch
  10. Water garden during establishment period and maintain as needed

1. Site Inventory
  A. Definition of a site inventory
    1. Locating site feature
2. Identifying problems
3. Identifying positive attributes
  B. Procedure
    1. Start with a plat of your property
      a. Make a map of the attributes of the site using a graph paper with either 1/8” or ¼” grid
b. Gather measuring and writing tools
    2. Record site data (draw locations and information on base map)
      a. Slope
        - Figure out how steep (how high does the land go over a set horizontal distance?)
      b. Exposure (which way the slope faces)
c. Moisture/water issues and distribution on property  
        i. The locations of areas which are wet during a rain (flow paths and puddling)
ii. Areas that are wet 2-3 days after a typical 1” rain
iii. Areas that are wet 5-7 days after a typical 1” rain
      d. Sun/shade locations
e. Soil type
        - (from the County soil maps and/or soil analysis sent to State Extension Service Soil lab)
      f. Existing plants
        1. Plants to keep
          i. Appropriateness
ii. Desire to keep
        2. Plants to go
          i. Unhealthy plants
ii. Exotic invasives
iii. Misplaced plants
      g. Identify your planting zone/physiographic area in the Chesapeake Bay Watershed (USDA Hardiness Zone 5 – 7, Heat Zone7-3)
        1. Mountain
2. Piedmont
3. Coastal Plain
      h. How people move through the area
i. Views
j. Noise


2. Site analysis

  A. Review inventory information and assign + and – to the information
B. Determine optimal area for rain garden based on:
    1. Moisture/water issues
2. How people move through the area/ who will see it
3. Other design considerations such as views, wildlife
  C. Determine which plant list to use based on:
    1. Light
2. Moisture
3. Soil types
4. Planting Hardiness Zone and physiographic region
5. Desired maintenance practices


3. Garden Design Concept Development


Is based on inventory, analysis and observation/inspiration
Is an organizing idea which is translated into spatial/garden layout
Is used as a basis for selecting a garden template
  B. Design Vocabulary
    1. Principles and Elements of Design
      a. Principles -
        i. Unity – what ties it all together; can be done via the elements of design
ii. Balance –
          - Formal is symmetrical/ axial
- Informal is a symmetrical and non axial but appears stable
        iii. Accent – a contrasting element is used for emphasis
      b. Elements – the building blocks of design
        i. Color
          - Influence of color on mood
- Influence of color on wildlife
- Seasonal variations
        ii. Form/ plant habit – the overall shape of a plant and is predictable
iii. Texture – creates depth and emotive effects
          - Seasonal variations
- Overall/ dominant
        iv. Scale – puts the garden in human perspective
v. Line – moves the eye
          - Plants have “lines”
- Beds have bedlines

vi. Value – how light or dark a plant is; influences perception of garden mood


4. Garden Design &/or Choose a Garden Template
  A. Decide on the theme of your garden and look at templates to see which matches your design ideas best
  B. Layouts/Templates
    1. Border Garden
      a. Perennial Border – 130 SF
b. Screening with fragrance – 256 SF
c. Red, White and Blue, Low Maintenance – 200 SF
d. Townhouse divider/shared garden – 130 SF
e. Deer Resistant – 200 SF
f. Tree hedgerow – 903 SF
g. White, Blue and Yellow, Low Maintenance – 200 SF
    2. Butterfly Garden
      a. Vegetated Swale – 250 SF
b. Perennial Border – 130 SF
    3. Formal layouts
      a. Rain garden Parterre – 384 SF
b. Roses and friends – 252 SF
c. Entry Garden – 113 SF plus 72 SF permeable pavers
d. For the birds – 450 SF
e. Screening with fragrance – 256 SF
f. One Nice Tree – 192 SF
    4. Informal layout with two sided viewing
      a. Tree hedgerow – 903 SF
b. Curved Border – 550 SF
c. White, Blue and Yellow, Low Maintenance – 200 SF
    5. Four season interest – color/texture/form
      a. Corner rain garden – 150 SF
b. Curved Border – 550 SF
c. Screening with fragrance – 256 SF
d. One Nice Tree – 192 SF
e. Entry Garden – 113 SF plus 72 SF permeable pavers
f. Roses and friends – 252 SF
g. Rain garden Parterre – 384 SF
h. White, Blue and Yellow, Low Maintenance – 200 SF
i. Townhouse divider/shared garden – 130 SF
j. For the birds – 450 SF
k.Tree hedgerow – 903 SF
    6. Fragrance
      a. Screening with Fragrance – 256 SF
b. Roses and friends – 252 SF
    7. Herbaceous Plants
      a. Perennial Border – 130 SF
b. Deer Resistant – 200 SF
    8. Color emphasis
      a. Perennial Border – 130 SF
b. White, Blue and Yellow, Low Maintenance – 200 SF
c. Deer Resistant – 200 SF

5. Plant lists by Zone and Physiographic Region for selection for use in rain gardens (more lists in plant list document)           

Plant Lists



Success in a Soggy Garden, The GreenMan Montgomery County, Maryland DEP


6 . Garden installation and care
  Essential Information 
    Mark your utilities before you dig
Know your soil time and amend to a minimum depth of 12”
Choose the right plant for the right place
  Preparing for Planting
    Construction guidance
      Check the various online resources listed in this and other documents on the website for specific procedural methods.
Lay out your garden with a hose or string and mark where all the plants are to go before you dig, buy plants or get your amendments.
Gather your materials before you start to dig and minimize any walking on the amended soil throughout the construction and subsequent time.
  Planting your Garden 
    Layout the plants according to the plan before your start to dig,
Dig holes and install plants; an inch of the rootball may be above the final level of the garden.
Water all plants well.
Add 3” of mulch around all the plants; do not pile mulch on the stems of the plants.
  Caring for your rain garden 
    Installation and first season 
      Watering practices 
        Water less frequently but longer. Water until you have added 1” of water and do this once a week for the first season. In subsequent seasons, you will not need to water at all except in periods of prolonged dryness. To determine how long it takes to add an inch of water, place a measuring cup in the garden and set your sprinkler on. When the measuring cup holds 1” of water, then you have watered the appropriate amount of time.
      Weeds, Mulch and other cultural issues 
        Weeding is important to do and to be vigilant about. Do not use herbicides in a raingarden; it will degrade the water quality you are trying to improve.
Mulch will need to be refreshed annually. Check your depth of mulch before adding more. It should be 3” deep. If the mulch is 3” deep, do not add more unless you remove some first.
        Perennial care
          Perennials will typically need to be divided every three years.
Cut back perennials in the fall.
        Shrub care
          This varies with the shrub but generally, prune flowering shrubs immediately after they bloom. If you wish to prune for a specific shape, prune out some of the interior of the shrub before you reduce the overall size of the shrubs.
    Maintenance schedule 
      This will vary by the type of garden and by the zone the garden is in. It is often helpful to tie maintenance tasks like mulching and pruning to a holiday (e.g. cut back perennials between Halloween and Thanksgiving) Keep a garden journal the first year and note when you do various maintenance tasks. This will give you a maintenance template for subsequent years.
  Ways to enhance the garden 
    Garden Art
Seasonal additions


Rain Garden Manual for New Jersey, The Native Plant Society of New Jersey

Pages 1 - 24, Pages 25 -48

Rain Gardens of West Michigan Saving the Great Lakes One Garden at a Time


Student BaySavers Projects Build Your Own Rain Garden



How to design a rain garden

Rain garden network

The Harpeth River rain gardens for Backyards site gardens.html

Build a rain garden

Hardiness zones map:

Heat zone map:

Bioretention Sizing