Rain Gardens

Photo © Chesapeake Bay Program

A rain garden can be any garden that you plant to catch excess storm water on your property– you can design it to suit your taste! Rain gardens filter pollutants (like excess nitrogen and phosphorous) from surface water before they have a chance to reach our aquifers, and they absorb 30% more runoff than a lawn. By reducing erosion, pollutants, and flooding, your rain garden will benefit aquatic wildlife in your watershed.

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Photo © Megan Funk, Cornell Department of Landscape Architecture

When it comes to rain gardens, it’s all about infiltration. The best place for a rain garden is down-slope from buildings in a place that will intercept water from your downspout before it drains into the street or sewer (see schematic). The point of a rain garden is to catch and hold runoff; a crescent shape design works like a catcher’s mitt to stop water in its tracks.

Rain Garden Schematic

Photo © Roger Bannerman & Ellen Considine

A rain garden can be built in the front or back yard. Pick a pleasing shape for the rain garden. Crescent, kidney, and teardrop shapes seem to work well. Rain gardens should be located at least 10 feet from the house, on a gentle slope that catches downspout water.

Rain Garden in Duluth, MN

Photo © eXtension Gardens, Lawns, and Landscapes

What thrives in a rain garden? Try native wetland plants that tolerate frequent saturation, like sedges, cattails, or joe pye weed. For other plant ideas, consult a professional local landscaper or contact your local cooperative extension office. What if rainfall is less plentiful in your locale? Even though a rain garden in a desert ecoregion will look very different from a rain garden in a subtropical ecoregion, they carry out the same function–to help rainwater find its way from the surface into the ground. Your erosion-fighting rain garden only needs to be watered while it’s getting established, which means less watering for you later. And as the plants’ roots grow and penetrate the soil, your rain garden will actually function better with age.

Rain Barrel at Work

Put a rain barrel to work for you. Use the water however you like.

Photo © arbyreed
Tip: The average rainfall in your city may be highly influenced by extreme years (such as droughts or floods). If rainfall is highly variable where you live, use 80% of your city’s average rainfall as your estimate of a “normal” year.

Rain gardens don't have to be elaborate affairs. This small corner was designed to soak up the rain delivered via chain from the roof.

Photo © burkhardt reiter

Another option for both wet and dry climates is harvesting rainwater with a rain barrel. One inch of rain on one square foot of roof area yields ~0.62 gallons. To calculate how much water you could potentially collect, multiply your roof’s area by your annual average rainfall and then multiply this number by 0.62. For example, the average annual rainfall in Ithaca, New York is 36.7 inches. If a roof in Ithaca is 2,000 square feet, then multiplying 2,000 square feet x 22.75 gallons/square feet gives us 45,508 gallons! In Ithaca, that represents a savings of $22,811 (assuming you could catch it all)! For that much water, you’d need a cistern (but that’s another article)! Based on these crude calculations, we think investing in a simple rain barrel is worth your while! Just position your rain barrel(s) underneath your downspout(s) and attach a hose to the faucet near the bottom. Voila! You’re ready to water your bird-friendly garden.

Have a Rain Garden to Map?


Photo ©

In the toolshed, choose “second” for mapping a habitat. Rain gardens are lumped together with bioswales and bioretention cells–all of which are considered “Stormwater Management”. Once you have mapped this area, you can tell us more about this habitat, like the specific type of feature that it is, the run-off source, the % native plants used, and the run-off source size.

Photo ©