Rain gardens beautify water runoff—here’s how to make one

Rain gardens are attractive solutions to water problems, turning poor drainage or rain gutter runoff into a beautiful, easy-care garden showpiece. They slow down stormwater so it doesn’t run off your yard and into the street and storm sewers, helping to reduce lawn bare spots and erosion due to fast flows, all while watering your garden.

Rain gardens also filter stormwater through the soil before it flows out to storm sewers, making your local streams, ponds, and lakes cleaner. Even better, most rain gardens are low-maintenance, don’t need watering, and encourage birds, butterflies, and pollinators to visit your yard. Here’s how to make a rain garden in your yard.

What is a rain garden?

In their simplest forms, rain gardens are shallow, bowl-shaped spots or depressions in your yard planted with flowers, shrubs, or grasses that thrive in waterlogged soil and in droughts. Rainwater collects in a rain garden during storms, then gradually seeps into the soil over a day or two after the rain ends—too fast for mosquitoes to lay eggs.

Most residential rain gardens are fairly compact, ranging from 60-square-feet to 180-square-feet. They can be any shape like a straight rectangular flower bed along a walkway, a circle of flowers in a low spot in a yard, or a crescent along a slope.

What all rain gardens have in common is that they’re made of soil which drains well after a storm. If you’re planning a rain garden for the low spot in your yard where there’s always a puddle, you’re going to need to spend time digging up the soil and amending it to make the site drain faster.

How to make a rain garden

Step 1: Identify a water-logged area or low spot in your yard

Look for a site in your yard where water drains from impermeable surfaces that don’t absorb water like your roof, patio, deck, driveway, or sidewalk. Keep the rain garden at least 10-feet away from your house’s foundation so water won’t drain into your basement; you can use a gutter extension to direct water to your rain garden. Just make sure to clean your gutters regularly. Keep rain gardens away from septic systems and tall trees which might get their roots damaged.

Step 2: Test the soil and add extra nutrients as needed

For a rain garden, you want soil that drains within a day or two after storms. To test your soil, dig a hole six inches deep and fill it with water. If the water drains in less than 24 hours, the soil is suitable for a rain garden. If it doesn’t drain within 24 hours, you may have clay soil, and you’ll need to amend it (add different materials) to make it drain.

Soil is made up of a mixture of three types of particles: sand, silt, or clay. Sand is made of the largest particles, clay is the finest particles, and silt particles are the in-between size. If your soil has a lot of clay or silt, it can drain slowly, and if you dig it when it’s wet, it may become a hard, compact lump.

You may need to add garden sand and compost to make sure your rain garden will drain. Never add sand alone to clay soil or you’ll end up with a mixture like concrete. Instead, try mixing volumes of 50% sand, 30% compost, and 20% existing soil down to six inches deep for new rain gardens in clay soil.

Step 3: Now, it's time to add rain garden plants

The key thing to remember is that plants for rain gardens need to be able to withstand sitting in standing water for up to two days and during periods of drought, since the site where they are planted may drain completely in between showers. Fortunately, a large variety of native plants are adapted to exactly these conditions and will thrive with little attention.

Plant flowers and shrubs that do best in drier conditions at the edge of your rain garden, and water-loving plants at the center, which will stay damp the longest as your rain garden drains.

Below are some of the easiest rain garden plants to grow in American rain gardens with average garden soil, adapted to hardiness zones four to seven (areas where the minimum winter temperature is somewhere between -30°F to 10°F. For more plant possibilities, check out the Environmental Protection Agency's waterwise plant list by state.

Here are rain garden plant ideas to control stormwater runoff, depending on where you live

Rain garden plants for the dry zone

• Anise hyssop (Agastache foeniculum): Butterfly milkweed (Ascelpias tuberosa) grows cheerful bright yellow-orange blooms on 2-foot plants in zones three to eight in midsummer, and provides food and flowers for Monarch butterflies, and nectar for hummingbirds. Pink swamp milkweed (Asclepias incarnata) prefers moister conditions; plant it in the wet zone in your rain garden.

• Coreopsis (Coreopsis tinctoria): Also known as tickseed, this plant with fluffy yellow flowers also comes in red, orange, white, or pink. It grows in hardiness zones five through nine, and individual varieties can persist in zones two through 11.

• New England asters (Symphyotrichum novae-angliae): These rain garden plants bloom in shades of purple, lilac, and pink from late summer until frost on 3-foot to 4-foot stalks in zones three to nine. They’re especially well-adapted to dry sites. New York American aster (Symphyotrichum novae-belgica) is a related flower with larger flowers; the “Purple Dome” variety grows in a mounded shape with fringes of purple-petaled flowers with orange centers.

Rain garden plants for the middle zone

• Blue false indigo (Baptisia australis): This flower blossoms into a 3-foot bush in early summer in zones three to 10. If purple isn’t your jam, go for white false indigos instead.

• Boltonia (Boltonia asteroides) stars: These produce mounds of white daisy-like flowers in midsummer on 3-foot stalks, and can keep blooming until frost in zones four to nine. The pointed, grayish-green leaves are a good foil for purple flowers like blue false indigo.

• Japanese maples: These plants are grown for their colored, lace-like leaves, not their flowers, and vary from 5-feet to 25-feet high at maturity; check the label carefully and plant for their ultimate height, not the size they are today. For small sites, pick a dwarf variety like deep red Pixie Dwarf. Most Japanese maples are hardy from zones five to eight.

Rain garden plants for the wet zone

• Blue flag iris (Iris Versicolor): This blooms in late spring with big, showy purple flowers with yellow and white veining. Hardy in zones three to eight, blue flag iris thrive in damp rain garden bottoms.

• Elderberry (Sambucus nigra): This grows rafts of small scented white flowers, then purple-black berries known for their medicinal value – and attractiveness to migrating birds. The “Black Lace” hybrid grows up to 6-feet to 8-feet tall in zones three to seven with dark, deeply-cut leaves and pink flowers; “Adams” is comfy in zones three to eight, and can grow to 10-feet tall with conventional green leaves.

• Royal ferns (Osmunda regales): Ferns like to keep their feet wet, and grow happily in shade as well as sunny spots in zones three to 10. Count on a maximum height of 2-feet to 6-feet depending on how much sun it gets.