Winter 2019
By Jennifer Leach
Environmental Education and Sustainability Coordinator
Department of Parks, Recreation, and Culture

Pretty rain garden with signRain gardens have become popular in recent years and for good reason. Not only can these gardens help alleviate flooding and erosion on your property, they can add beauty to your landscape, attract birds and pollinators, and help filter harmful pollutants that would otherwise run off into the Puget Sound.

But is a rain garden right for YOUR yard?

While rain gardens might look a lot like a traditional garden on the surface, they’re actually designed and constructed with unique characteristics that enable them to do their primary job – to collect surface water and let it soak into the ground. For a rain garden to function properly, certain conditions need to be met. Site drainage patterns, soil drainage rates, the location of utilities and infrastructure, and how much space you have available are just a few things to consider when deciding whether a rain garden is right for you.

To get started, consider the following questions:

1.  How does water move through your landscape?

Water that drains from rooftops, driveways, and patios can all be routed to a rain garden. It’s important to keep in mind that water will flow to your rain garden by gravity, so you’ll need to locate the garden downslope of these features. Pay particular attention to areas on your landscape that may be eroding, as erosion patterns can be a good indicator of which way water is moving across your site. Once you know where your water is coming from and where it’s going (or could be routed to), you can start thinking about the right location for your rain garden.

2.  What’s underground?

Constructing a rain garden requires excavating an area two to three-and-a-half feet deep, so you’ll want to know where your underground utilities and infrastructure are located when considering the right location. You can request to have your utilities located and marked at no cost by calling 811. Septic systems and wells all have specific setback requirements, so be sure to check local codes before deciding on a location for your rain garden.

3.  How well does your soil drain?

Once you think you’ve found the right spot for your rain garden, you need to make sure that the location you’ve chosen drains well enough to soak up all the water draining to your garden. A high groundwater table, compacted soils, or soils with a lot of clay can all cause poor site drainage.

The rainy months during the winter are the perfect time to test your soil drainage. Dig a hole 36” deep in the location where you’d like to put your rain garden. If water seeps in from the sides or bottom, that means you have a high groundwater table and you’ll need to find another location for your garden. Next, conduct a soil percolation test in a nearby spot; step-by-step instructions can be found here. If your drainage rate is less than 0.1 inches per hour, you’ll want to consider another location for your rain garden.

Other factors you’ll want to consider when deciding if a rain garden is right for your yard is the proximity to building foundations, the location of bluffs and steep slopes that could be prone to landslides, or in an area where healthy trees and other vegetation are already doing a good job of filtering and storing water.

If you can’t find the right spot for a rain garden on your property, there are lots of other tools you can use to help manage water on your property including replacing lawn with native plantings, harvesting rain water using rain barrels and cisterns, installing permeable pavement, or simply amending soils with compost and mulch. You can learn more about these tools, and pick up a copy of the Rain Garden Handbook for Western Washington in the City of Edmonds’ Green Resource Room located on the second floor of City Hall.

To learn more about rain gardens in Edmonds or to schedule a group tour, call Jennifer Leach at 425-771-0227 or email jennifer.leach@edmondswa.gov.