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Rain Garden Resources from Penn State Extension

Penn State Extension has many resources for property owners, municipal staff, and anyone else who wants to learn more about building, planting, and maintaining rain gardens.

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Updated:

October 3, 2025

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This rain garden infiltrates water from a downspout visible in the upper right corner of the picture; Photo: Andy Yencha, Penn State

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Rain gardens are landscape features that an increasing number of homeowners, businesses, and local governments are installing to reduce the stormwater that flows off their properties. These infiltration basins come in many shapes and sizes, but all rain gardens collect stormwater runoff from roofs, parking lots, or other hard surfaces so some of this water will soak into the ground instead of flowing onto nearby properties or into municipal storm sewer systems. Rain gardens contain plants (natives preferred) that provide many functions and benefits. The plants absorb stormwater, remove runoff pollutants, provide habitat for pollinators and other wildlife, and beautify the places where we live and work. Penn State Extension has developed a rich collection of materials related to building, planting, and maintaining rain gardens.

Why Build a Rain Garden?

Rain gardens manage stormwater, which is a growing problem in Pennsylvania and many other parts of the United States. Excess runoff triggers erosion, destroys aquatic habitat, pollutes water, and causes flooding and flood-related property damage. Rain gardens can help fix these problems.

How to Build a Rain Garden

Basic rain gardens can be installed in residential areas to capture modest amounts of stormwater from downspouts, driveways, and backyard patios. These homeowner gardens are often small (under 100 square feet), just a few inches deep, and very often do not require soil amendments if the existing ground drains well enough. Complex rain gardens, sometimes containing special soil mixes and underground drainage, are increasingly found in urban areas to capture heavy runoff flows from parking lots, roads, and commercial buildings. Before digging your rain garden, Penn State Extension recommends doing a simple percolation test to ensure adequate drainage. Contact your County Extension office for more information.

Rain Garden Plants

Rain gardens are called "gardens" because they contain a variety of plants that help them manage stormwater and provide other important benefits. Plant selection, especially for the do-it-yourselfers with minimal gardening knowledge, can seem overwhelming. Penn State Extension has several resources to make the process easier, including information about soil testing, which, if performed, can provide useful information on soil fertility and pH that might influence your final plant selection.

Soil Testing

Plant Field Sheets

Plant selection is especially important. Matching plants with the sunlight, soil, and moisture conditions of your rain garden is the first step in the plant selection process. Penn State Extension Educators recommend considering plants with varying characteristics to make your garden attractive through all seasons. Choose plants based on factors like mature height, overall appearance, bloom time and color, spreading habits, any unique benefits they offer, such as providing food for pollinators, and availability at local garden centers or through mail-order vendors.

Maintaining rain gardens, especially proper plant identification through all four seasons, so they do not get accidentally removed as weeds, can be challenging at times. Therefore, it is important to know what each plant looks like during the various stages of growth. We created rain garden plant articles to provide more information as you begin to select, plant, and maintain your rain gardens.

The plants are arranged by preferred moisture conditions. Wet/Moist zone plants prefer places that are always wet and may not do well in gardens with excellent drainage. Moist zone plants can tolerate some dry conditions but do best in sites where soils are usually moist, but not consistently saturated. Moist/Dry zone plants are the workhorses of most rain gardens because they can tolerate both wet and dry conditions. Dry zone plants can survive occasionally being wet, but do best in well-drained soils. These plants are often planted on the high sides of rain gardens.