Install a Rain Garden to Improve Water Quality

Whitney Laritson | February 14, 2026

If you have trouble with water runoff damaging your garden, or you just want to do your part to protect your local rivers, then you'll want to explore creating a rain garden.

Rain gardens are a beautiful and practical way to control storm water runoff. They are simply a garden planted in a depression at the base of a slope that collects and holds rainwater, allowing it to slowly seep into the ground, rather than flow into roads and waterways. These are not ponds or even swampy areas. In fact, a well-made rain garden is designed to drain excess water in less than two days (which is good news if mosquitoes are a problem).

They are so effective, and so beneficial for stormwater management and improving water quality, that some homes can earn tax breaks for creating one.

Benefits of Rain Gardens

The primary benefit is its ability to control urban runoff , especially during major rain storms. Urban runoff comes from our roofs, driveways, lawns, sidewalks and roads, and is full of pollutants like pet waste, fertilizers and pesticides.

Left unchecked, this urban runoff can contribute to damaging flash floods and polluted watersheds. Build a rain garden to slow the polluted water from reaching storm sewers.

Officially known as “bioretention areas,” these were first introduced to developments in the 1990s in an effort to save money on water runoff treatments. Studies on these early rain gardens showed an impressive 75–80% reduction in stormwater runoff during an average rain storm.

Here are some other amazing benefits:

They prevent erosion. Water runoff is caught and absorbed before it has a chance to cause damage.
They are beautiful. Full of sedges, grasses and flowers, rain gardens have a lovely cottage garden appearance.
They save money. They cost a fraction of the cost of a typical lawn to plant and require very little water.
They’re easy to landscape. Low-maintenance by design, you'llprimarily using tough, native plants that can handle both dry and wet periods.
They protect your home. Rain gardens collect excess rain water away from your home, preventing issues like wet basements, mosquito-breeding puddles and foundation issues.
They support wildlife. Birds, insects and even amphibians can call a rain garden home.

One of the greatest things about rain gardens is how easy they are to create and landscape. In fact, Mother Nature does most of the work for you.

Elements of a Rain Garden

Swale or piping, to guide water runoff
A slope down to the rain garden - a 2% grade is ideal
Decorative stones and boulders
Berm to hold the runoff
Deep rooted plants, ideally suited to a rain garden environment

Where to Put a Rain Garden

In order to capture the most runoff, it needs to be strategically placed. When scouting for the perfect place, look for a natural depression, or low-lying area of your property where stormwater flows and pools. Just make sure you place it well away from your house; more than 10 feet away is ideal.

No matter what, do not put your rain garden over a septic tank or utility lines, and always call 811 before you start digging.

Plant Selection

Rain Garden Planting Zones

The best plants for rain gardens actually vary depending on where you plant them. Every rain garden has three planting zones:

Center - where water pools and soaks into the soil. Water-loving plants that can handle soggy soil do best here.
Slopes/sides - a little drier, but still susceptible to pooling water. Versatile plants that can take both dry and soggy soil will thrive here.
Top - the driest area, that needs deep-rooted drought tolerant plants to hold together and keep the berm in place.

It's best to plant plugs or small plants, not from seed, which easily washes away.

Here is a list to get you started. Remember, check your local USDA growing zones, as well as your average annual rainfall. Some plants suggested for slopes in a wetter climate, for example, may do better in the center for drier climates.

Best Plants for Center

Best Plants for Slopes

Bee balm
Aster
Silky dogwood
Wild geranium

Best Plants for Top

Rain gardens are a truly win-win landscaping project that benefit everyone, from the homeowner, to the community at large. Incorporate one into your own garden and enjoy the many benefits.

Happy Gardening!

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Frequently Asked Questions

How do you install a rain garden step by step?

To install a rain garden, start by identifying a low-lying area at least 10 feet from your home's foundation where water naturally collects, ideally at the base of a slope. Dig a shallow depression about 6 inches deep and direct runoff toward it using a swale or piping from your roof, driveway, or lawn. Fill the basin with a well-draining soil mix, then plant it with tough native plants that tolerate both wet and dry conditions, such as sedges, native grasses, and flowering perennials suited to your hardiness zone. For best results, plan your rain garden to drain completely within 48 hours to prevent standing water and mosquito breeding.

How deep should you dig a rain garden based on your yard's slope and soil type?

The depth of your rain garden depends on both slope and soil type, but most rain gardens should be dug between 4 and 8 inches deep. For yards with sandy, well-draining soil, a shallower depth of around 4 to 6 inches is usually sufficient, while clay-heavy soils that drain slowly may require a deeper basin of 6 to 8 inches to hold water long enough for proper absorption. A steeper slope generally means more water volume rushing in, which also calls for a deeper, wider basin to handle the load. Test your soil's drainage rate by digging a small hole, filling it with water, and measuring how many inches drain per hour, then use that figure to finalize your depth before breaking ground.

How does a rain garden filter and manage stormwater runoff?

A rain garden is planted in a depression at the base of a slope, where it captures stormwater runoff from roofs, driveways, and lawns and allows it to slowly percolate into the ground rather than flow into storm sewers and waterways. Studies on early rain gardens showed a 75 to 80 percent reduction in stormwater runoff during an average storm, and a well-designed rain garden drains completely within 48 hours, preventing mosquito breeding. The plants, typically tough natives like sedges, grasses, and wildflowers, help filter pollutants such as fertilizers, pesticides, and pet waste before they reach local waterways. To get started, identify a natural low point or slope on your property where runoff collects, and plan to install a swale or piping to direct water into your planting area.

How do you calculate the right size rain garden for your roof or driveway drainage area?

To size a rain garden, measure the square footage of the impervious surface draining into it, such as your roof section or driveway, then calculate the rain garden at roughly 20 to 30 percent of that drainage area. For example, a 1,000 square foot roof section would call for a rain garden of approximately 200 to 300 square feet. Soil type matters too, since sandy soils drain faster and allow for a smaller garden, while clay soils require a larger one to handle the same volume. Start by testing your soil drainage, then use your local cooperative extension service's rain garden sizing calculator for precise measurements tailored to your region's average rainfall.

What plants grow best in a rain garden that experiences both flooding and dry spells?

Rain gardens experience two extremes, so you need tough, adaptable native plants that can handle temporary flooding as well as drought. Sedges like Pennsylvania Sedge (Carex pensylvanica) and native grasses such as Switchgrass (Panicum virgatum) are excellent choices, along with flowering perennials like Blue Flag Iris, Black-eyed Susan, and Joe-Pye Weed, all of which thrive in USDA zones 4-9 and tolerate wet feet followed by dry periods. Focus on plants native to your specific region, as they are already adapted to local rainfall patterns and soil conditions. Visit naturehills.com to browse native plants suited to your zone and build a rain garden that looks great while doing real environmental work.

Should you use native plants in a rain garden, and which species perform best?

Native plants are strongly recommended for rain gardens because they have deep root systems adapted to your local soil and climate, allowing them to handle both flooding and drought with minimal care. Sedges, native grasses, and flowering perennials like swamp milkweed, Joe-Pye weed, black-eyed Susan, and cardinal flower are proven performers in most rain garden plantings across a wide range of zones. These plants establish quickly, require little supplemental water once rooted after their first season, and support local wildlife including pollinators and birds. Browse Nature Hills' selection of native perennials and grasses to find species suited to your specific region and zone.

How far should a rain garden be from your house foundation or septic system?

A rain garden should be located at least 10 feet from your home's foundation and a minimum of 25 feet from any septic system or well. Placing it too close to the foundation can redirect water toward your basement rather than away from it, undermining the garden's primary purpose. Choose a spot that naturally collects water at the base of a slope, and confirm the site is well away from underground utilities before you begin digging.

What soil mix should you use when building a rain garden to improve drainage and filtration?

For optimal drainage and filtration, a rain garden typically performs best with a engineered soil mix of roughly 50 to 60 percent sand, 20 to 30 percent topsoil, and 20 to 25 percent compost. This blend allows water to infiltrate quickly enough to drain within 24 to 48 hours while still retaining enough organic matter to support healthy plant growth. Avoid heavy clay soils, which will cause water to pool and potentially kill your plants. Test your existing native soil first, and if drainage is poor, excavate 18 to 24 inches deep and replace or amend with this recommended mix before planting.

How do you prevent a rain garden from holding standing water for too long or draining too quickly?

The key is proper site selection and soil preparation. Choose a location with a gentle slope and amend heavy clay soils with a mix of sand, compost, and topsoil to achieve a well-draining blend that allows water to infiltrate within 24 to 48 hours. If your garden drains too quickly, adding more organic matter will help retain moisture long enough for pollutants to filter out. Test your soil drainage before planting by digging a hole, filling it with water, and confirming it empties within two days, then adjust your soil mix accordingly before installing plants.

How do you maintain a rain garden through the seasons to keep it healthy and functional?

Rain gardens are designed to be low-maintenance by nature, but seasonal attention keeps them performing at their best. In spring, remove any accumulated debris and dead plant material, check that the basin is still properly graded, and replenish mulch to a depth of 2 to 3 inches to suppress weeds and retain moisture. During the growing season, water newly installed plants during dry spells for the first one to two years until they establish, after which native sedges, grasses, and perennials typically thrive on rainfall alone. Each fall, cut back spent vegetation, inspect inflow and outflow areas for erosion or clogging, and divide overcrowded plants to keep the garden draining efficiently.