How to Build a Rain Garden

Here at Sunday, we love things that look good AND do good. Lush lawns. Microclover. Pollinator-friendly plants. And the do-gooder du jour: rain gardens!

What Is a Rain Garden?

Rain gardens are low-lying areas filled with native plants and strategically located to capture runoff from impervious surfaces like roofs, driveways, walkways, and parking lots. During times of increased precipitation, rain gardens will collect that prized moisture, rather than allowing it to run off of those hard surfaces into a storm drain.

What Are the Benefits of Rain Gardens?

Gardens provide a space for you and your family to relax, recreate in nature, and enjoy beautiful blooms year after year. But rain gardens are more than just a pretty space. They have some major practical benefits, primarily the management of stormwater and runoff.

 

Why do we care about runoff? Impervious surfaces have a habit of collecting pollutants like sediment, oil, radiator fluid, and other yard debris. When water pools on these surfaces and runs off into storm drains, it can eventually make its way into lakes, rivers, and wetlands—taking the pollutants with it. Not good! 

 

Furthermore, developed areas like cities are more prone to flooding because the water has nowhere to go but to storm drains—and, subsequently, the municipalities’ sewer system. When storm and sewer systems get overwhelmed, it can result in untreated wastewater entering our local natural waterways during periods of heavy rainfall. Also not good.

 

This is all especially relevant in light of increasing urbanization (as impervious surfaces replace green spaces) and in light of increasingly erratic weather patterns. By capturing rather than wasting rainwater, we can make the most of our resources.

 

In addition to preventing flooding and filtering water, rain gardens have several other benefits:

 

  1. Mending drainage issues. Beyond keeping water from pooling on your paved surfaces, rain gardens can help the areas of your lawn where water collects and grass struggles to grow. 
  2. Increasing the value of your lawn. Beautiful landscaping increases your enjoyment as well as the financial value of your property. According to the EPA, some communities offer tax breaks for residents who install rain gardens. Call your local municipality to find out if you would qualify!
  3. Educating all ages. Rain gardens provide a DIY educational space for your family to explore. What better way to help kids build greater connections to the natural world and learn to garden sustainably?
  4. Sheltering pollinators. By utilizing native plants in your rain garden, you’re providing critical habitat and forage for insects, birds, and other wildlife.

 

Why Use Native Plants in a Rain Garden?

It’s no secret that we love native plants here at Sunday. Once established, they require little supplemental watering, and for that reason alone they make great rain garden plants—and a great choice for eco-conscious yards. Part of this water-resourcefulness comes from their natural adaptations—like thriving in saturated soils—and from their deep root systems, which, conveniently, can also absorb excess water. 

 

They also help prevent eutrophication (aka, nutrient pollution) in waterways, because those deep roots hold soil in place. Less erosion = less sediment and nutrient runoff.

Lastly, native plants are regionally adapted species that have evolved with local species over thousands of years—so they provide critical habitats for insects, pollinators, birds, and other wildlife that rely on these verdant corridors in urban areas.

How to Build a Rain Garden

Rain garden design need not be overwhelming. In fact, this is the part where you get to have some fun, be creative, and leave a mark on your landscape.

 

Rain gardens work well in a variety of locations, but they’re especially useful for regions that experience heavy rain and snow melt, and for yards that have low-lying, flood-prone areas. Sound like you? Keep reading!

 

1. Assess your yard. Make note of areas where water collects from rainfall and snow melt. You may also consider gutter drop-out locations, paved surfaces, low zones, and areas with poor drainage.

2. Select the right location. Most stormwater tends to run off impervious surfaces like roofs, driveways, and walkways so it’s likely your rain garden will do well if placed where runoff tends to collect or puddle.

 

Sunday ProTip: Plant your garden at least 10 ft. away from building structures to avoid issues with water damage or excess moisture.

 

3. Figure out the direction of flow. If the planting zone naturally collects water, you likely don’t need to alter the direction of water flow. However, if you need to prevent water from collecting on a hard, flat surface, you can install a drainage pipe or spout to direct the flow of water directly into the rain garden. 

4. Select appropriate species. Plant natives that require varying levels of moisture (this garden may not always be saturated) and tolerate the appropriate levels of light for the space you’re planting in. A good rule of thumb for starting out is 2–3 sedge species, 1–2 grass species, and 3–4 flowering species, all native to your region.

5. Map out your planting area. Account for the appropriate spacing between plants (they don’t just grow up, they grow out too!) and cluster plants in groups of 3+ of the same species. Keep in mind that you can plant a rain garden more densely than other gardens to slow water movement and allow roots to knit together and stabilize the soil. It’s also a good idea to place your thirstiest plants in the lowest part of the garden (where the most moisture will accumulate), surrounded by a medium-moisture area and drier areas along the edges.

6. Remove the first layer of vegetation. Remove any grass or plant vegetation that is covering the area you’ll be planting into. The process will help your native plants during establishment as it will limit competition for resources (think water, sunlight, root growth). When you do this, it’s good to remove some top soil to set aside and save for later.  

7. Dig the right depth. In order for a rain garden to hold water efficiently, you’ll need to ensure the depth of the planting area reaches a level depth of 4-8 inches. Ensuring the plot has the same level depth will allow for runoff and rainwater to be absorbed within the planting area, avoids drowning the plants and limits overflow during heavy rains. After you ensure level depth, fill the zone with a 2-1-1 mix of high quality topsoil, sand and compost

 

SUNDAY PRO TIP: Utilize any extra soil to help form a berm, or mounded border, to limit water from overflowing over sloped or downhill areas adjacent to the garden. Cover with rocks, mulch or grass to limit sediment loss or erosion.

 

8. Go forth and plant. Using your design and depths, plant your native species accordingly. We really appreciate this cool app that shows how to integrate aesthetics and structurally conscious design into native gardens. (Note: this app focuses on species adapted to Connecticut. Make sure you’ve selected plants appropriate for your region.)

9. Return topsoil and amend soil. Place any leftover topsoil back into the garden and cover with mulch to limit weeds, hold soil in place and ensure the area holds good levels of moisture. While native plants won’t require tons of maintenance long-term, they need to be kept moist and weed-free as the plants establish. 

10. Finally, maintain as needed. Hand-pulling occasional weeds, adding and maintaining mulch around the new plantings, and making sure water drains appropriately are all things you might need to do from time to time. Monitor your garden and add native plants or seeds as you’d like! 

 

Ready to get growing? Check out our tips for maintaining your garden bed before and after it gets established. Happy planting!

Cited Sources

How and Why to Build a Rain Garden. University of Minnesota Extension.

Lovell, S. T. and D. M. Johnston. Designing Landscapes for Performance Based on Emerging Principles in Landscape Ecology. Ecology and Society.

Goggin, Patrick. Native Planting Companion Guide. Wisconsin Department of Natural Resources.

Rain Gardens. Natural Resources Conservation Service.

What Is Green Infrastructure? U.S. Environmental Protection Agency.

What to Plant. U.S. Environmental Protection Agency.

Wheeler, Justin. Rain Gardens Are a Win/Win. Xerces Society.

Managing Wet Weather with Green Infrastructure Municipal Handbook, Incentive Mechanisms. Environmental Protection Agency.