How to Build a Rain Garden in Your Backyard

An easy-to-build backyard rain garden is a work of art that will help you solve your drainage and runoff issues.


| July/August 2012



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Whether your backyard is large or small, rain gardens enhance the landscape while improving runoff problems and the ecosystem.

Brenda Carson/Fotolia

Tired of that muddy puddle in the middle of the yard, or that washed-out mini-gulley that forms whenever a downpour loads up your home’s downspouts? If so, it might be time to get a handle on all that runoff and put it to good use by learning how to build a rain garden. These shallow saucer-shaped gardens, commonly described as “nature’s water filters,” are designed to capture excess runoff that can potentially wreak havoc on your soil and pollute waterways. All you need to create your own rain garden is a well-designed plan, a handful of native plants, and some good old-fashioned elbow grease.

How rain gardens work

Rain gardens are designed to catch storm runoff from rooftops, patios, sidewalks, roads and other impervious surfaces. During a storm, rain gardens will fill with a few inches of water that gradually filter into the ground. When properly designed and constructed, these structures can hold water for around 24 hours and will not attract mosquitoes — they’re much more likely to attract birds and beneficial insects.

Rain gardens can be helpful wherever water runoff is an issue. Ideally, you will want to situate the rain garden in between the source of the runoff and the runoff destination.

Before you break ground, make sure the garden is at least 10 feet from any buildings or structures, and at least 25 feet from any septic system drain field. Also be sure to avoid underground utility lines (call 8-1-1 at least 48 hours before digging), and if you have trees on your property, avoid disturbing established root systems.

Conduct a soil evaluation

Sandy and loamy soils work best for these backyard havens since they tend to drain well. Clay soils can become waterlogged and may not be suitable for a rain garden. Test the drainage of potential sites by digging a percolation test hole that is at least 8 inches wide and 8 inches deep. Fill the hole with water and let stand. Ideally, the water should drain at a rate of about an inch every hour. If you are working with hard clay soil that won’t drain, remove it and replace it with a mix of approximately 60 percent sand, 20 percent topsoil and 20 percent compost.

Calculate rain garden size

A rain garden can be almost any size, but most residential rain gardens range from 100 to 300 square feet. Many are the shape of a saucer or kidney bean, with the largest side facing the source of runoff. Use site conditions as a natural guide in shaping the garden. Rain gardens are generally 4 to 8 inches deep. Anything deeper than 8 inches may pond water, and rain gardens less than 4 inches deep may not provide enough water storage for proper infiltration. The slope of the land should help determine the depth of the garden.





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