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Rain Gardens


Build a Rain Garden
Rain gardens are an attractive green solution to reduce storm water pollution and improve overall water quality. Storm water becomes polluted when it runs over pavement and comes into contact with automotive fluids, sediment, trash, pet waste, and lawn fertilizer.  Ordinarily, this storm water “runoff” flows directly to rivers, lakes and streams without treatment. By directing storm water runoff to a rain garden filled with native plants, pollutants can be absorbed by the deep plant roots instead of contaminating our rivers, lakes and streams.

What is a Rain Garden?
A rain garden is a “garden shaped like a bowl.”  A fancier way to explain it is that it is a shallow, constructed depression that is planted with deep-rooted native plants & grasses. It is located in your landscape to receive runoff from hard surfaces such as a roof, a sidewalk and a driveway. Rain gardens slow down the rush of water from these hard surfaces, holds the water for a short period of time and allows it to naturally infiltrate into the ground.

A rain garden can be thought of as a personal water quality system because it filters the runoff from your roof and lawn and recharges the groundwater.

A rain garden also conserves municipal water resources by reducing the need for irrigation.

Rain gardens are a beautiful and colorful way for homeowners, businesses and municipalities to help ease stormwater problems.  There is a growing trend by municipalities and homeowners to incorporate natural processes to help relieve flooding and pollution.

Rain gardens provide several benefits:

  • Vegetation and soils within the rain garden use physical and biological processes to remove contaminants carried by stormwater runoff.
  • Infiltrating stormwater into native, underlying soils helps mimic natural drainage processes and reduces the volume of stormwater runoff. 
  • Stormwater runoff reduction improves the physical and biological integrity of receiving streams by reducing stream bank erosion and negative effects on aquatic communities.
  • Rain gardens improve the aesthetics of an area compared to conventional infrastructure. 


For more information, visit:
http://www.epa.gov/greeningepa/stormwater/edison_rain_garden.htm

 

Want a Rain Garden?

Contact Koren Taylor at koren.taylor@talgov.com to learn more today!



How to Plant a Rain Garden

Building a Rain GardenStep One:
Siting and Sizing the Rain Garden
Where should the rain garden be located?
What size and shape should the rain garden be?

Step Two:
Building the Rain Garden
Digging the Garden
Leveling the Garden
Making the Berm

Step Three:
Planting and Maintenance
Planting the Garden
Maintaining the Garden
Helpful Tips for Rain Garden Design and Planting
Two Simple Soil Tests

 


 
RAIN GARDENS: A How-to Manual for Homeowners

Rain Garden Homeowners in many parts of the country are introducing rain gardens - landscaped areas planted with wildflowers and other vegetation that can capture and soak up rainwater in their yards to help improve the environment. Rain water flowing from the roof, lawn, paved driveway, walkway, etc. fills the rain garden with the first few inches of rain from a storm, minimizing the amount of water entering a storm drain or nearby stream. For the next several hours (up to a day), the water slowly seeps into the ground and is filtered by the soil and plants in the garden. A rain garden allows approximately 30% more water to soak into the ground compared to a conventional lawn. Building a rain garden on your property is a beautiful way to help Slow the Flow and improve the quality of water in nearby lakes and streams.

The garden, consisting of plants, mulch, loose soil and sometimes a layer of small gravel, utilizes several methods to absorb and disperse water. Plant roots absorb water for use in the biological processes of plant metabolism, where it is transpired or "breathed" out through the leaves into the atmosphere. Water not used by the plant roots is absorbed into the loose soil. As water moves downward through the mulched layer, chemical and biological processes filter and break down many pollutants found in water that runs off the land after a storm. Over time, excess water evaporates into the atmosphere.

This manual provides homeowners and landscape professionals with the basic direction needed to design and build rain gardens on residential lots. Guidelines presented in this manual also can be used to treat roof runoff at commercial and institutional sites. However, rain gardens for parking lots, busy streets or other heavily paved areas where stormwater may require pretreatment should rely on more technically engineered designs. For more information about rain gardens in those areas, please go to the stormwater management agency in your local community.

It is a good idea to look through this entire manual before you get started. In our Rain Garden Plant List you will find a list of plants to help you select the right plant for the spot you have chosen for your rain garden.

Happy Gardening!

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Why are rain gardens important?
As cities and suburbs continue to displace forests, wetlands, and open spaces, increased stormwater runoff from impervious (non-absorptive) surfaces such as roofs and pavement has become problematic. Stormwater runoff increases flooding and carries pollutants from streets, parking lots and lawns into local lakes and streams. Local municipalities are challenged to fund costly stormwater treatment facilities in order to clean the water. This "personal pollution" from our lawns and property contributes to the pollution of local waterways. Rain gardens can help improve the quality of our local waters and the environmental health of our communities by reducing the amount of stormwater leaving our yards. While an individual rain garden may seem like a small thing, collectively several rain gardens can produce substantial neighborhood and community environmental benefits.

Facts about rain gardens:

  • Rain gardens increase the amount of water that filters into the ground, recharging the groundwater supplies from which we draw our drinking water.
  • Rain gardens help provide protection from flooding and aid in solving drainage problems.
  • Rain gardens help protect our streams, lakes and rivers from pollutants such as lawn fertilizers, pesticides, oil and other substances that wash off lawns, roofs, and paved areas to be carried in stormwater. The rain garden can collect and filter most of these pollutants, protecting and cleaning the water.
  • Rain gardens help protect structures and other vegetation in your yard from flowing water.
  • Rain gardens enhance the beauty of yards and neighborhoods.
  • Rain gardens provide valuable habitats for birds, butterflies and many beneficial insects.
  • Rain gardens are fairly simple to build, and yield lots of benefits.

Does a rain garden form a pond?
No. The rainwater should soak into the ground and be utilized by the vegetation so that the garden is dry between rainfalls. (Note: Some rain gardens can be designed to include a permanent pond, but that type of rain garden is not addressed in this publication.)

Does a rain garden provide a breeding ground for mosquitoes?
No, the opposite. Mosquitoes need several days to lay and hatch eggs. Standing water in the garden should last for only a few hours after most storms. Mosquitoes are more likely to lay eggs in birdbaths, plant pots, and old tires than in a rain garden. Also, rain gardens attract dragonflies, and dragonflies eat mosquitoes.

Do rain gardens require a lot of maintenance?
No. Rain gardens can be maintained with little effort once the plants are established. As with any garden, some weeding and watering will be necessary in the first two years, and perhaps some thinning in later years as plants mature.

Is a rain garden expensive?
It doesn't have to be. The cost is site specific and will vary depending on who does the work and what plants you select. To keep costs down you can invite family and friends to help build the garden or start with smaller planted areas.

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STEP ONE: Siting & Sizing the Garden
This section covers rain garden placement, size, depth, length, width, soils and slopes. The best way to ensure a successful rain garden project is to follow the instructions in this section.

Where should the rain garden be located?
Home rain gardens can be located ten feet or more away from the house to catch roof runoff, or further out in the lawn to collect water from the lawn, roof and driveway. When considering placement of your rain garden, think about how the garden can be integrated into existing landscaping. Also, pay attention to views from inside the house as well as those throughout the landscape. Determine how far away or how close you want your rain garden to be to outdoor gathering areas. For example, why not locate it near a porch or patio where you can enjoy the colors and fragrances?

 

A rain garden can be built in the front or back yard.

To help decide where to place your rain garden, consider these points:

  1. The garden should be at least ten feet from the house so that infiltrating water doesn't seep into the foundation.
  2. Do not place the garden directly over a septic system or drainfield.
  3. The goal of a rain garden is to encourage additional water infiltration. Wet patches in your yard may already be retaining water. You may want to add rain garden plants to that area and choose an additional location for your rain garden.
  4. It is better to build the garden in full or partial sun. For a list of plants appropriate for shade and sun, please see the plant list in Appendix A.
  5. Be careful not to put it directly under a large tree.
  6. Digging will be much easier if you choose a more level or gently sloped part of the yard. Slope is discussed later in this section.
Rain gardens should be located at least 10 feet from the house on a gentle slope that catches downspot water.

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What size and shape should the rain garden be?

The size of your rain garden will depend on the following factors:

  • What type of soil do you have?
  • How much roof and/or lawn will drain to the garden?
  • How deep will it be?


What type of soil makes up your rain garden site?
It is very important to identify your soil type: sandy, silty or clay. Sandy soils provide the fastest infiltration; clay soils have the slowest. Since clay soils take longer to absorb water, rain gardens in clay soils must be larger than rain gardens in sandy or silty soils. If the soil feels gritty and coarse, you probably have sandy soil. If your soil is smooth, but not sticky, you have silty soil. If it is very sticky and clumpy, you probably have clay soil. Refer to Appendix B for two simple soil tests to determine your soil type.

If you have questions about your soil, call the Leon County Agricultural Extension Office at (850) 606-5202.

How large is the area draining to your rain garden?
In choosing your rain garden site, determine the size of the area draining into the garden. The larger the drainage area, the larger the size of the rain garden. There is a little guesswork in determining the size of a drainage area, especially if a large part of the lawn is uphill from the proposed garden site. Use the suggestions below to estimate the drainage area. See Example #1, below.

For rain gardens located 10 to 30 feet from a downspout:

  1. When the rain garden is in the vicinity of the house, almost all of the water will come from the roof and downspout. Walk around the house and estimate what percent of the roof feeds to that downspout. Many houses have four downspouts, each taking about 25 % of the roof's runoff.
     
  2. Next, to determine the size of your roof, find your home's footprint: the area (square footage) of the first floor. If you don't already know it, use a tape measure to find your home's length and width. Multiply the length and width together to find the approximate square footage (area) of your roof. You don't have to be exact, just get a good idea of the size of your roof.
     
  3. Finally, multiply the approximate roof area by that part (percentage) of the roof that feeds to the downspout draining to the rain garden (Step 1). This is the roof area that drains to the rain garden.

 

 

EXAMPLE # 1
Caluculating the Roof Area Draining to Your Rain Garden.

Your house is 60 feet long x 40 feet wide, so the roof area is 2,400 square feet.

Calculate roof area:
60 feet x 40 feet = 2,400 square feet.

*You estimate that a particular downspout collects water from 25 % of the roof, so you multiply 2,400 x 0.25 to get a downspout drainage area of 600 square feet.

Calculate drainage area:
2,400 sq. ft. x 25% = 600 square feet draining from that portion of the roof into the rain garden.

*If your lawn is sloped, also note Example #2.

   

For rain gardens further than 30 feet from the downspout:

  1. If there is a significant area of lawn uphill that also will drain to the rain garden, this lawn area should be added to the roof drainage area. First, determine the roof drainage area using steps 1-3 above for a rain garden 10 to 30 feet from the downspout.
     
  2. Next, find the area of the lawn that will drain to the rain garden. Stand where your garden will be and look up toward the house. Identify the part of the lawn sloping into the rain garden.
     
  3. Measure the length and width of the uphill lawn. Multiply these two figures to find the lawn area in square feet.
     
  4. Add the lawn area to the roof drainage area to find the total drainage area that will be directed to your rain garden. If your patio or driveway also drains to the rain garden, be sure to measure them as well and add that square footage to your total area.

* For rain gardens farther than 30 feet from the downspout, this total area will be the drainage area you use when calculating the surface area of your rain garden (explained below).

 

 

 

How deep should the rain garden be?
A typical rain garden is between 4 and 8 inches deep. A rain garden deeper than 8 inches may pond with water too long, resembling a hole in the ground, and possibly creating a safety hazard for anyone who accidentally steps into it. Additionally, a garden less than 4 inches deep will require a large surface area to contain water runoff generated from heavier rainstorms.

No matter the depth of the garden, the goal is to level the ground surface of the garden. Digging a very shallow rain garden on a steep lawn will require bringing in extra topsoil to raise the downhill border of the garden to the same height as the uphill part of the garden. As your slope gets steeper, it is easier to dig the garden a little deeper to level the ground surface.

 

 

Finding the Slope of Your Yard
The slope of the lawn should determine the depth of the garden.

Find the slope of your lawn by following these steps:
  1. Pound one stake into the ground at the uphill end of your rain garden site, and pound a second stake in at the downhill end, about 15 feet away.
  2. Tie a string to the bottom of the uphill stake and run the string horizontally across the garden site to the downhill stake.
  3. Using a string level or a carpenter's level, make the string level and tie the string to the downhill stake at that height.
  4. Measure along the string between the two stakes for the horizontal width.
  5. Now measure the vertical height on the downhill stake between the ground and the string.
  6. Divide the vertical height by the horizontal width and multiply the result by 100 to find the lawn's percent slope. If the slope is more that 12 %, it's best to find a more gently sloped site, or talk to a professional landscaper.
MATERIALS LIST:
String
2 wooden stakes
String level or carpenter's level
Ruler
Possibly a calculator

EXAMPLE #2:
Slope & Depth
The horizontal distance of the string between the stakes is 180 inches. The string's vertical height on the stake is nine inches. Divide the height by the distance between stakes and multiply by 100 to find your lawn's percentage slope.

                                 9 in. height = 1/20 or 0.05
                                180 in. width

                                   0.05 X 100 = 5% slope

Using the slope of your lawn, select the depth of the rain garden.

Percent of Your Slope Recommended Depth of Your Rain Garden
Less than 4% 3 to 5 inches deep
5 to 7% 6 or 7 inches deep
8 to 12% about 8 inches deep

Based on a 5% slope, build the rain garden 6 to 7 inches deep. Remember to include the downspout and lawn drainage calculation in Example #1 to determine the total square footage (surface area) of the rain garden.


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How much land should the rain garden require?
The surface area or square footage of the rain garden can be almost any size, but time and cost will always be important considerations in sizing decisions. Any reasonably sized garden will capture some stormwater runoff, and every bit you capture helps.

A typical residential rain garden ranges from 100 to 300 square feet. Gardens smaller than 100 square feet will limit the number of plants you can plant. The larger the rain garden, the more opportunity you have to plant a variety of plants. A large garden of more than 300 square feet will take longer to dig and will be more difficult to make level.

The sizing guidelines described in this manual are based on a goal of controlling 100% of the runoff for the average rainfall while keeping the size of the rain garden reasonable. A goal of retaining all of the water that falls on your roof, yard and driveway helps compensate for any error that may creep into the design and construction of the project.

If you follow the guidelines presented in this manual and decide the calculated surface area is just too large, it is perfectly okay to make the garden smaller or create a series of rain gardens. The rain garden can be up to 30% smaller and still control up to 90% of the annual runoff. On the other hand, it is fine to make the garden bigger than the guidelines indicate. Any actions you take will help to reach the ultimate goal of slowing the flow and reducing the amount of water that drains from your property.

Now that you have estimated the drainage area, soil type and depth for your garden, use Table 1 or Table 2 to determine the garden's surface area. Use Table 1 if the garden is 10 to 30 feet from the downspout; use Table 2 if it is further than 30 feet from the downspout.

Table 1
Rain Gardens LESS than 30 feet from the downspout

Table 2
Rain gardens MORE than 30 feet from the downspout
 

3-5 in. deep

6-7 in. deep

8 in. deep

 

Size factor for all depths

Sandy soil

0.19

0.15

0.08

Sandy soil

0.03

Silty soil

0.34

0.25

0.16

Silty soil

0.06

Clay soil

0.43

0.32

0.20

Clay soil

0.10

Source: University of Wisconsin Extension Service
  1. For the size factor for the soil type and rain garden depth, refer to Table 1 or Table 2.
  2. Multiply the size factor by the drainage area you calculated above. This number is the recommended rain garden surface area.
  3. If the recommended garden surface area is much more than 300 square feet, distribute the area requirement into two or more smaller rain gardens.
EXAMPLE #3:
How to Determine Surface Area of the Garden
(Remember to use both slope and area drainage calculations where appropriate.)

Your lawn has a 5% slope, so you will have a 6 inch deep rain garden. Your lawn is silty and your rain garden is 10 to 30 feet from the downspout, so, by referring to Table 1, you see that a size factor of 0.25 is recommended. You multiply the downspout drainage area*, 600 square feet (from Example #2), by 0.25 to find the recommended rain garden area: 150 square feet.

                              600 square feet x .25 (Table 1) = 150 sq. feet

*If your drainage area includes an area of lawn, the driveway, etc. as well as roof downspout, remember to use the total drainage area in your calculations.

Choose a size that is best for your yard. Remember that these are only guidelines. The size of the garden also depends on how much room you have in your yard, how much runoff you wish to contain and how much you want to spend.


How long and wide should the rain garden be?
Before building the rain garden, think about how it will catch water. Runoff will flow out of a downspout and should spread evenly across the entire front border of the garden. The base of the garden must be as level as possible so water doesn't pool at one end or spill out before it has a chance to infiltrate.

The longer side of the garden should face uphill - that is, the front facing edge of the garden should be perpendicular to the slope and the downspout. This way the garden catches as much water as possible. Still, the garden should be wide enough for the water to spread evenly over the whole bottom surface and provide enough space to plant a variety of plants. A good rule of thumb is that the garden should be about twice as long (perpendicular to the slope) as it is wide.

When deciding the width of the garden, remember the slope of the lawn. Wide rain gardens and those on steep slopes will need to be dug deeper at the top end in order to be level. If the garden is too wide, you may need to bring in additional soil to fill in the downhill portion of the rain garden. Experience shows that making a rain garden about 10 feet wide is a good compromise between the effect of slope and how deep the garden should be. A rain garden should have a maximum width of about 15 feet, especially for lawns with more than an 8% slope.

EXAMPLE #4:
How to Determine the Length of the Rain Garden
  1. Choose a rain garden width suitable for your lawn and landscaping, for example, ten feet.
  2. Divide the square footage of your garden by its width to find your garden's length.

You want a rain garden that is ten feet wide, so divide 150 square feet (from Example 3) by 10 foot width to calculate your rain garden's length at 15 feet.

 

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STEP TWO: Building the Rain Garden
Now that the size and place for the rain garden are set, it's time to get a shovel and start digging. Working alone, it will take approximately six hours to dig an average-sized garden. If you make it a family project, it will go much faster, possibly only an hour or two. Remember to call before you dig. It is very frustrating to cut through an underground wire or cable and it will really slow your project.

If you are building the garden into an existing lawn, you can reduce your digging time by removing the sod first. Sod is easy to remove with a square shovel and should be useful elsewhere. Also, the best time to build the garden is in the fall. It's easier to dig and the plants are more likely to thrive.

Digging the Rain Garden

  1. While digging the garden to the correct depth, heap the soil around the edge to form a berm - a low dirt "wall" around three sides of the garden that keeps the water in during a storm. On a steeper lawn the lower part of the garden can be filled in with some soil from the uphill half and extra soil might need to be brought in for the berm.
     
  2. Create the shape of your rain garden by laying a garden hose around the area you wish to use. Remember that the berm will go outside the hose. Next, put stakes along the uphill and downhill sides, lining them up so that each uphill stake has a stake directly downhill. Place a stake every five feet along the length of the garden.
     
  3. Begin at one end of the garden and tie a string to the uphill stake at ground level. Tie it to the stake directly downhill so that the string is level. Work in five-foot-wide sections, with only one string at a time. Otherwise the strings will become obstacles.
     
  4. Start digging at the uphill side of the string. Measure down from the string and dig until you reach the depth you want the garden to be. If the garden will be four inches deep, then dig four inches down from the string. Refer to Figure 5 for guidance.
     
  5. If the lawn is almost flat, you will be digging at the same depth throughout the garden and using the soil for the berm. If the lawn is steeper, the high end of the garden will need to be dug out noticeably more than the low end and some of the soil from the upper end can be used to fill in the lower end to make the garden level. Continue digging and filling one section at a time across the length of your garden until it is as level as possible.
     
  6. In any garden, compost will help the plants become established, and now is the time to mix in compost. A roto-tiller can make mixing much easier, but it is not necessary. If you do add compost, dig the garden one or two inches deeper than planned. Then add one to two inches of compost.

MATERIALS LIST:
Tape measure
Shovels, rakes, trowels
Carpenter's level
Wood stakes at least 2 feet long
Garden hose
A six-foot 2 x 4
Plants
Mulch


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Leveling the Rain Garden
One way to check the level of the garden is to just "eyeball" it. For more accuracy, follow these steps:

  1. When the whole area has been excavated to about the right depth, lay the 2x4 board in the garden with the carpenter's level sitting on top. Find the spots that aren't flat. Fill in the low places and dig out the high places.
     
  2. Move the board to different places and different directions, filling and digging as necessary to make the surface level.
     
  3. Once the garden is as level as you can make it, rake the soil smooth.


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Making the Berm
Water flowing into the garden will naturally try to escape over the downhill edge. A berm is critical to help hold the water inside the garden (look back at Figure 5). The berm is a "wall" across the lower border and along the sides of the garden. The berm will need to be the highest at the downhill edge, and should be as high as or slightly higher than the uphill edge. Moving along the sides up toward the front edge of the garden, the berm will gradually become lower and finally taper off by the time it reaches the top of the garden.

On a more gradual slope there should be plenty of soil from excavating the garden to use for a berm. On a steeper slope, most of the soil from the uphill part of the garden will be used to fill the downhill half and additional soil may have to be brought in for the berm. After shaping the berm into a smooth ridge about a foot across, tamp it down to compact the soil. It is important to have a strong, well-compacted berm, so tamp hard. The berm should have very gently sloping sides; this helps to smoothly integrate the garden with the surrounding lawn and also makes the berm much less susceptible to erosion.

To prevent erosion cover the berm with mulch, lay sod, or plant a ground cover. You can also use straw or erosion control matting to protect the berm while the grass becomes established. If you don't want to lay sod or mulch over the berm, you can also plant drought tolerant vegetation or winterize the berm with rye grass.

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STEP THREE: Planting & Maintenance
Planting the rain garden is the fun part! Lists of suggested plants are included in Appendix A. Use these for ideas, but don't be afraid to be creative. There is no single best way to plant a garden. Anyone who has ever done any gardening will have no problem planting a rain garden. What follows are a few basic reminders.

Planting the Garden

  1. Select one or more types of plants that have a well established root system. Nursery-propagated plants are best and three or four types of plants should be enough.
     
  2. Try to have at least a rough plan for where each plant will be placed. Lay out the plants as planned, keeping appropriate distances between plants.
     
  3. Dig each hole twice as wide as the plant and deep enough to keep the crown of the plant level with the existing grade (just as it was in the cell pack or container). Make sure the crown is level and then fill the hole and firmly tap around the roots to eliminate air pockets.
     
  4. Apply mulch evenly over the bed, about two inches thick.
     
  5. Place plant labels next to each individual grouping. This will help identify your young plants from non-desirable species (weeds) when you weed the garden.
     
  6. As a general rule, plants need one inch of water per week. Use a simple rain gauge to measure the amount of water the plants are receiving. Be sure to water the garden immediately after planting and continue to water several times each week (unless it rains) until the plants become established. You should not have to water your garden once the plants begin to thrive on their own.

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Maintaining your Rain Garden
Weeding will probably be necessary for the first year or two, as with any new garden. Remove by hand only those plants you are certain are weeds. Try to take the weeds out roots and all. Weeds may not be a problem in the second season, depending on the variety and tenacity of the type of weeds present. By year three and beyond, your rain garden plants will begin to mature and will out-compete the weeds, although weeding isolated patches might still be needed occasionally.

After each growing season, the stems and seed heads can be left on for winter interest, wildlife cover, bird food and reseeding. Once spring arrives and new growth is four to six inches tall, cut back all tattered plants.

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HELPFUL TIPS FOR Rain Garden Design & Planting

  • While rain gardens offer a highly functional way to help protect the water quality and prevent flooding, they are also gardens and should become an attractive part of your yard and neighborhood. Think of the rain garden in the context of your home's overall landscape design.
     
  • When choosing plants for the garden, it is important to consider the height of each plant, bloom time, bloom color and the garden's overall texture. Use plants that bloom at different times to create a long flowering season. Mix heights, shapes and textures to give the garden depth and dimension. This will keep the garden looking interesting even when few flowers are in bloom. Native plants make good choices because they are accustomed to the regional climate and rainfall patterns and will acclimate to the rain garden easily.
     
  • When laying out plants, randomly clump individual species in groups of three to seven plants to provide a bolder statement of color. Use odd numbers when determining how many to plant in a mass. Make sure to repeat these individual groupings to create repetition and cohesion in a planting.
     
  • Try incorporating a diverse mixture of sedges, rushes and grasses with your flowering species. This creates necessary root competition that will allow plants to follow their normal growth patterns and not outgrow or out-compete other species. In natural areas, a diversity of plant types not only adds beauty but also creates a thick underground root matrix that keeps the entire plant community in balance. Once the rain garden has matured and your plants have established a deep, thick root system, there will be little change in species from year to year and weeds will naturally decline.
     
  • Don't forget to mulch. Composted yard debris and leaves are best. Mulch helps keep your soil moist, suppresses weed growth, stabilizes soil temperatures, and reduces erosion and soil compaction.
     
  • Finally, consider enhancing the garden by using local stone, ornamental fencing, garden benches or additional flower plantings. This will help give the new garden unintentional and cohesive look and provide finished appearance that the neighbors will appreciate.


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Simple Soil Tests to Determine if Your Soil is Right for a Rain Garden.

Percolation Test:
This simple procedure can determine your soil's porosity, or infiltration rate - how fast it will drain. Remove both ends from a 46 oz. can (like a large juice can) and mark a line two inches from one end. Pound the can into the soil so that the line is level with the land surface. Pour one quart of water into the can and time how long it takes to drain into the soil.

Drainage Time

Soil Condition

Conditions for a Rain Garden

2 minutes or less excellent porosity and air circulation This soil offers the best conditions for a rain garden.
Two to 8 minutes somewhat compact or dense Drainage will be slower than in soil that is less compact, but acceptable for a rain garden.
8 minutes or more overly compact or dense It will be challenging to install a rain garden in this area because drainage will be very slow.

Test for Clay: Take a handful of soil and dampen it with a few drops of water. After kneading the soil in your fingers, squeeze the soil into a ball. If it remains in a ball, then work the soil between your forefinger and thumb, squeezing it upward into a ribbon of uniform thickness. Allow the ribbon to emerge and extend over your forefinger until it breaks from its own weight. If the soil forms a ribbon more than an inch long before it breaks, and it also feels more smooth than gritty, the soil has too much clay for a rain garden. You should consider that the area will drain poorly and should plan for more permanent ponding or select a more porous site.

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This manual is a product of the TAPP (Think About Personal Pollution) Campaign, which is funded by a grant from the U.S. Environmental Protection Agency to the City of Tallahassee through the Florida Department of Environmental Protection and administered by the City of Tallahassee Stormwater Management and Environmental Policy & Energy Resources Divisions.
                                    
Original concept and illustrations for this manual were derived from Rain Gardens - A how-to manual for homeowners, produced by the University of Wisconsin Extension Service. Material has been revised and edited for application to the North Florida and Gulf Coastal climes by Nancy Miller with the assistance of Yasmeen Barnes-Nkrumah, Thure Caire and Master Gardeners Pam Sawyer, Dr. Paul Elliott, Dr. Ed Schroeder.  Additional illustrations, photos and page layout by Maria Balingit.





City of Tallahassee