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What is a Rain Garden and How to Build One in Your Yard

rain garden gutter drainage runoff system

Did you know that a simple, attractive addition to your yard can help protect the environment and improve water quality? Enter the rain garden, a unique landscape feature that is gaining popularity for its myriad benefits. Let’s explore the ins and outs of rain gardens, from “what is a rain garden” to designing, installing and maintaining one in your own yard.

Short Summary

  • Most rain gardens use native plants that will increase plant diversity and help the environment.
  • Rain gardens absorb and filter rainwater runoff, providing environmental protection.
  • They reduce storm water runoff, prevent sewer overflows, conserve water and prevent flooding.
  • You should carefully consider site location, size & depth and plant selection.
  • Regular maintenance of your rain garden will ensure its long term success.

Understanding Rain Gardens

rain garden in between two sidewalks in a residential neighborhood
Rain gardens catch rain water for plants instead of letting it run off into storm drains. Source: USEPA Environmental-Protection-Agency, Public domain, via Wikimedia Commons

Rain gardens are specialized gardens composed of native shrubs, perennial and flowers. You construct it in a shallow depression on a natural incline. Its main purpose is to temporarily store and absorb rainwater runoff that flows from rooftops, driveways, patios or lawns. Unlike a water garden, a rain garden is usually dry, except when filled with water after a rainfall.

Rain gardens serve an important role. They manage rainwater runoff, filter pollutants and provide habitat for pollinators. They collect and store rainwater until it can soak into the ground, with the plants and soil filtering out pollutants.

The Purpose of Rain Gardens

Rain gardens:

  • Prevent storm water from running off and reaching nearby streams, rivers and ponds.
  • Gradually distribute water into the native soils through rain garden drains.
  • Prevent rainwater from entering the sewer system. This reduces the likelihood of sewer backups or overflows.
  • Safeguard rivers and streams from polluted storm water runoff.
  • Eliminates up to 90% of nutrients and chemicals from rainwater runoff. This provides an extra layer of protection to waterways.

The effectiveness of a rain garden depends on its design and proper maintenance at the chosen rain garden site. This is how rain gardens work to protect our environment.

Creating your own rain garden is an amazing way to manage rainwater runoff on your property. It acts as an artificial depression or facilities a pathway to one. You’ll contribute to environmental protection while enhancing the beauty of your landscape.

Benefits of Rain Gardens

Beyond their primary purpose of managing rainwater runoff, other benefits include:

  • Filtering pollutants in runoff
  • Providing habitat for wildlife
  • Enhancing water quality
  • Diminishing the risk of water pollution and sewer overflows
  • Conserving water
  • Augmenting plant diversity
  • Preventing flooding
  • Replenishing groundwater reserves
  • Adding beauty and value to your landscape through the use of native plants and attractive design.

By installing a rain garden on your property, you are not only contributing to environmental conservation, but also creating a functional and visually appealing landscape feature. You can enjoy the beauty of your rain garden while knowing that you are actively making a difference in the health of our waterways and ecosystems.

Key Components of a Rain Garden

rain garden in a residential neighborhood holding water
Rain garden in Seattle, WA, reduces peak flooding by retaining stormwater runoff. Source: USEPA Environmental-Protection-Agency, Public domain, via Wikimedia Commons

When planning a rain garden, it’s essential to consider three key components: native plants, soil and drainage.

Each of these elements plays a crucial role in the overall function and success of your rain garden, ensuring it effectively manages rainwater runoff and contributes to a healthy ecosystem.

A rain garden’s plants are native to your geographic location. Natives are the backbone of a rain garden, as they are well-adapted to local conditions. They provide essential soil stabilization, water recharge and pollutant filtration benefits. Soil considerations are vital for proper drainage and overall garden health, while drainage and infiltration factors ensure efficient water collection and absorption.

Native Plants

The use of native plants in rain gardens is important for several reasons.

  • They are well-adapted to local conditions requiring less maintenance and are more likely to thrive.
  • Natives play a significant role in soil stabilization, water recharge and pollutant filtration.
  • Native plants have strong root systems, allowing them to better utilize the water and nutrients available in their native soils than non-native species.
  • Their deep roots also help to improve the overall drainage and infiltration of water in the rain garden.

By choosing native plants for your rain garden, you are not only creating a low-maintenance and sustainable garden, but also supporting the local ecosystem.

Learn more about native plants here.

Soil Considerations

Soil is another critical component to consider when planning a rain garden. Proper soil conditions are necessary for efficient drainage, ensuring that your rain garden effectively manages rainwater runoff. In some cases (like with clay soil), it may be necessary to amend the soil in your rain garden to enhance water infiltration.

Before starting work on your rain garden, it’s crucial to conduct a simple water percolation test (or perc test) to determine the soil drainage rate at the site.

illustration of a hole with a ruler measuring the water drainage
Conducting a perc test will let you know if you have slow, average or fast draining soil. This will help you determine the depth needed for your rain garden. Illustration by Pretty Purple Door, from the Plant Perfect Activity Book.

In my Plant Perfect Activity Book, I explain in detail how to conduct a per test with simple illustrations. But, in general, this test is pretty simple:

  • Dig a 12″ deep hole in the soil where you want your rain garden
  • Presoak the hole and let it drain.
  • Refill the hole with water and measure how much water drains in a 1 hour period.

This will let you know if your soil is slow, average or fast-draining.

  • If it drains under 1″ in an hour, it’s slow.
  • If it drains 1-3″ in an hour, it’s average.
  • If it drains over 3″ in an hour, it’s fast.

This will help you identify any potential drainage problems and make adjustments to the soil composition. This will ensure the long-term success of your rain garden.

Drainage and Infiltration

The drainage and infiltration aspects of rain garden design are essential for ensuring efficient water collection and absorption. Infiltration rain gardens control runoff volumes by gradually distributing water into native soils.

In other words: proper drainage is crucial for the success of a rain garden.

Your rain garden should drain within 24 hours after a storm.

Ideally, you want a percolation rate of at least 1″ per hour.

By carefully considering drainage and infiltration factors in your rain garden design, you can create a landscape feature that effectively manages rainwater runoff, reduces the risk of flooding and contributes to a healthier ecosystem.

Designing Your Residential Rain Garden

rain garden with grasses and decorative boulders
Beautifully designed rain garden with grasses and stones in Oregon. Source: Oregon Convention Center, CC BY 2.0, via Wikimedia Commons

Now that you understand the key components of a rain garden, it’s time to design one for your property. The design process involves several steps, including:

  1. Selecting a site for your rain garden
  2. Determining the size and depth of your rain garden
  3. Choosing the right plants for your specific conditions

By following these guidelines, you can create a beautiful and functional rain garden that will benefit both your property and the environment.

Keep in mind that your rain garden should be tailored to your specific property conditions and preferences. There is no one-size-fits-all approach to rain garden design, so don’t be afraid to get creative and make adjustments based on your unique needs and desires.

1. Site Selection

Choosing the right location for your rain garden is critical for its success. Factors to consider include soil type, slope and drainage. Ideally, a rain garden should be placed on the downside of a slope on your property to maximize water collection.

Make sure your rain garden is an adequate distance from buildings and structures to prevent potential water damage. Consult local resources for recommendations on the ideal distance between a rain garden and buildings in your area.

2. Size and Depth

Determining the appropriate size and depth of your rain garden is essential for effective water management. Most rain gardens are 3-6″ in depth. The size and ponding depth is determined by the impervious surface area you want to drain and your soil percolation rate.

Let’s get some definitions out of the way so this is easier to understand:

  • Ponding depth is the depth that water can pond before it flows out of the rain garden. It’s measured from the lowest point of the rain garden surface to the elevation of the outlet.
  • Impervious surface area is the area that needs to be drained into the rain garden (like the surface area of your roof).

The rain garden depth is determined by the soil percolation rate. This prevents the water from overflowing out of your garden.

  • If you have slow draining soil (<1″/hour), make the depth a minimum 3″.
  • If your soil is fast draining (>1″/hour), make the depth 3-6″.

The rain garden size is generally 10%-20% of the impervious surface area draining to the garden. The percentage depends on your pre-determined depth (see above).

For simple size calculations, use this 10/20 rule:

  • For a 3″ ponding depth, the rain garden size should equate to the impervious area to be treated divided by 10.
    • Example: 50′ × 40′ (rooftop area) = 2,000 sq ft (impervious rooftop surface area) /10 = 200 sq ft of rain garden
  • For a 6″ ponding depth, the rain garden size should equate to the impervious area to be treated divided by 20.
    • Example: 50′ x 40′ (rooftop area) = 2,000 sq ft (impervious rooftop surface area) /20 = 100 sq ft of rain garden
  • You can get more detailed size and depth info on the website.

These are just estimated calculations. You can round your numbers off (if needed).

3. Plant Selection and Placement

pink and orange flowering plants in a raingarden
Rain garden in the Allen Centennial Gardens in Madison, WI. Source: James Steakley, CC BY-SA 4.0, via Wikimedia Commons

Selecting and placing plants in your rain garden is an essential part of the design process. When choosing plants, consider their water uptake capacity and the type of soil in your rain garden. Native plants are an excellent choice, as they are well-adapted to local conditions and provide benefits, such as:

  • Soil stabilization
  • Pollutant filtration
  • Wildlife habitat
  • Increased biodiversity

When placing plants in your rain garden, consider factors such as sunlight, soil moisture and aesthetics. Grouping plants with similar water needs together can help ensure they thrive in their new environment. Don’t be afraid to get creative with your plant placement and design a visually appealing rain garden that reflects your personal style.

Installation and Costs

well designed rain garden with bushes and grasses outside a building
Beautiful rain garden design in Portland, OR. Source: EmilyBlueGreen at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

Once you’ve designed your rain garden, it’s time to consider installation options and costs. Complete your rain garden installation the DIY-way or by hiring a pro. The choice between the two will depend on your budget, expertise and available time.

It’s essential to weigh the pros and cons of each option, taking into account factors such as cost, time and the complexity of your rain garden design. Regardless of which option you choose, proper installation is crucial for the long-term success of your rain garden.

DIY vs. Professional Installation

DIY installation can be a more cost-effective option and provides a sense of accomplishment and personalization. However, it can be time-consuming. And, a lack of expertise may lead to potential issues down the road, like wet feet from improperly installed flooring.

On the other hand, professional installation offers the expertise and experience of a trained professional. This can save you time, but it may be more expensive. Ultimately, base the choice between DIY and professional installation should on your personal preferences, budget and the complexity of your rain garden design.

Cost Factors

The cost of constructing a rain garden can vary depending on several factors, including soil type, plant selection and property conditions.

Here are some cost estimates based on a 200 sq ft rain garden:

  • DIY installation materials can cost between $1-$5 per square foot ($200-$1,000).
  • A professionally designed and installed residential rain garden can cost between $12-$25 per square foot ($2,400-$5,000).
  • Commercial rain gardens can cost up to $40 per square foot ($5,000-$8,000).

Consider these cost factors and weigh the pros and cons of DIY vs. professional installation. This way, you can make an informed decision on the best approach for your rain garden project.

Rain Garden Maintenance

an elderly main weeding a garden with red flowers
For the first 2 years, you’ll have to provide water to your rain garden plants and weed as needed. Source: radekkulupa, via Pixabay

Proper maintenance is essential for your rain garden. During the first two years, it may need occasional watering and weed removal to help the plants become established. Once the plants are well-established, they should out-compete weeds and reduce maintenance.

Long-term maintenance includes:

  • Periodic inspections after heavy rain events
  • Plant care
  • General upkeep ensures your rain garden continues look great and function effectively.

First Two Years

During the first two years of your rain garden’s life, it’s crucial to provide adequate watering and remove weeds as needed. This will help your plants become firmly established. It will also help them (eventually) out-compete weeds, requiring less long-term maintenance.

When you dedicate time and effort to your rain garden’s maintenance in the early years, you’ll set the stage for years to come.

Here are some more strategies for weed prevention.

Long-Term Maintenance

For long-term maintenance, periodically inspect your rain garden, especially after heavy rain events. This will ensure it’s functioning properly with no damage or blockages.

Plant care is also crucial, including pruning, fertilizing and replacing plants as necessary.

By dedicating time to routine maintenance, your rain garden will remain a feature. And, provide enormous environmental benefits!


To help you successfully build and maintain your rain garden, here are some other resources and further reading:

These resources will hep you optimize your rain garden design for your specific region and ensure its long-term success.

Wrapping Up

Rain gardens are an attractive, eco-friendly and functional addition to any landscape. By understanding their purpose, key components and design principles, you can create a beautiful and effective rain garden tailored to your property and local environment.

Whether you choose a DIY or pro install, proper maintenance and care will ensure its long-term success. This way, your rain garden will benefit both your property and the environment for years to come.

Frequently Asked Questions

What is the point of a rain garden?

Rain gardens are an effective and beautiful way to reduce runoff. They capture rainwater, filter pollutants, protect wildlife and control soil erosion. They are cost-effective and can provide food and shelter for pollinators like butterflies.

Rain gardens are a great way to add beauty to your landscape while also providing environmental benefits. You can design them to fit any size yard and plant them with native plants that are best for your local climate.

What is a rain garden and how does it work?

A rain garden is a shallow depression that captures and filters rainwater runoff from impervious surfaces like rooftops, sidewalks and driveways. This allows pollutants to be naturally removed as the water slowly soaks back into the soil.

At the same time, it creates a beautiful landscape feature with plants and mulch.

What are the disadvantages of a rain garden?

Rain gardens can have several issues like drainage backups, flooding and increased erosion. These are usually due to improper design.

You can avoid these issues with proper design and maintenance. For example, direct water away from the house and other structures and ensure the soil can absorb the water.

What is the difference between a rain garden and a regular garden?

Unlike a regular garden, a rain garden absorbs and filters rainwater. It holds water during and following a rainfall event. This allows 30% more water to seep into the ground than a traditional lawn.

Planted with native vegetation, it’s a cost-effective way to reduce runoff from your property.

How do I determine the appropriate size and depth of my rain garden?

To determine the size and depth of your rain garden, consider the area you want to drain and the estimated runoff volume.

For example, if you want to drain a large area, you may need a larger rain garden than if you were draining a smaller area. If the runoff volume is high, you may also need a filter.

More About Native Plants

What Blooms with What?

Never know what to plant together? Find out with this FREE Plant Pairing Guide and become a pro at combining plants for the best garden design possible!

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