Rain garden benefits

According to WSU, a nationally recognized leader in the study of Low Impact Development who have lead the way in best rain garden practices, Rain gardens are an extremely effective way to reduce water pollution. Rain gardens act like native forests, storing, filtering and releasing cool, clean water to streams and rivers. Studies have shown that streets with rain gardens can stop 90 percent or more of the pollutants running off of roads, driveways and other hard surfaces. If you and your neighbors all installed rain gardens, you’d be doing a world of good in preventing oil, pesticides, fertilizers and other toxic chemicals from entering Puget Sound and harming the natural environment. Studies have shown that rain gardens bind-up metals to the mulch layer, and break down other toxins into safer components. You can feel good that your rain garden is one of 12,000 Rain Gardens, soaking up 160 million gallons of polluted runoff to protect our waterways!
Rain gardens act like a native forest by collecting, absorbing and filtering rainwater that runs off roof tops, driveways, patios and other areas that don’t allow water to soak in. Instead of rainwater puddling on your property, a rain garden captures channeled rain in a depression in the ground, and filters the water on-site, removing any oil, fertilizer, pesticides or other pollutants that would otherwise be dumped in the sewer. Rain gardens also prevent flash floods and erosion in streams by slowing down stormwater.
According to the Washington State Association of Realtors, a properly installed rain garden and attractive planting can be a nice addition to the value of a home, especially at resale. Because rain gardens reduce maintenance costs for homeowners, help prevent flooding and create eye-catching, low-maintenance landscaping they can easily pay for themselves in increased home value.

Building rain gardens

View the WSU video and Rain Garden Handbook available on the Resources page. They will help you decide. If you feel that “Do It Yourself” won’t work for you, contact a landscape professional with experience designing and building rain gardens. Before you hire someone, check references. Your homework will help get the rain garden you want at a cost that is right-and you might find there are parts that you’re comfortable doing yourself, which will save you money.
Rain gardens can be sized and shaped to fit in a variety of locations, however locate your rain garden where any water overflow can direct safely away from the home and neighboring property, and where water drains to the rain garden by gravity.* A contractor can help you find the best place for your rain garden, taking into account slopes, groundwater, utilities and drains.
A rain garden needs soil that drains well. It’s best to test soil drainage in the winter months. There are simple tests you can do to see if there is high ground water at your location, which you should avoid. In general, sandy soil drains well, and clay soil drains poorly. If you’re not sure what soil you have, you can learn more about how to perform specific soil tests at Stewardship Partners’ Events.
There are number of other low-impact development practices you can do to keep your stormwater on site and prevent polluted runoff. The least complex and costly alternatives are to make use of the water onsite if it does not endanger your home, outbuilding and neighbors. There are many water-loving plants that can be assembled into an attractive “bog garden.” Bog gardens are areas where the soil is waterlogged either naturally or artificially, creating a suitable environment for growing plants that thrive in moist soil. The International Carnivorous Plant Society has an excellent collection of resources for Pacific NW bog gardens at its website. Natural Life Magazine also has a very informative article on the design, construction and planting of a downspout Pacific NW bog garden. Download the article here (July/August 2007). You can slow the flow of water off of your property thus potentially reducing erosion and downstream flooding by amending soils with compost, creating swale gardens and developing a canopy garden with layers of water using plants. You can also position garden beds in such a way that they’ll capture the water running off your roof and lawn-for instance, making a buffer with beautiful plants at the boundaries of your property. Rain barrels and cisterns can be used to capture and temporarily store water from your downspouts. Just be sure to design enough capacity in your system because they overflow when full – this negates their usefulness for reducing flooding on your property. You can use the stored water to water your garden in summer. If you would rather infiltrate the water then you may need a larger or deeper rain garden or a dry well. You will need onsite professional advice in this case.
The Rain Garden Handbook for Homeowners has plant lists for each zone in a rain garden. You can select the plants you want by viewing other rain gardens, visiting your local nursery, or consulting a landscape designer. There is a special “bioretention mix” available from some bulk soil and compost providers such as Cedar Grove Composting, otherwise you can mix your own by adding 30 to 40 percent plant-based compost to a sandy soil. Mulch can reduce weed growth. Choose a course “hog fuel” (not bark) mix that will not float when the rain garden basin is filled. It can be found at bulk soil providers and often for free and from tree cutting services.
No. Because rain gardens are shallow and are only built on soils with sufficient drainage, they are designed to dry out before mosquitoes can reproduce.
Rain gardens are designed to infiltrate water in about a day. If it rains several days in a row, it is possible that your rain garden may have standing water until the rain stops and the water has time to soak in.


Costs vary from a few hundred to a few thousand, depending on a number of factors, like the size of the garden and whether you’re doing the project yourself, hiring a contractor, or a combination approach. Stewardship Partners has helped with a number of successful do it yourself projects that cost about $500. You can save money by purchasing smaller plants and watching them grow, or join conservation groups who salvage plants from new development sites. Volunteering some of the labor with the help of your neighbors, friends and family is also a great way to save money and have fun.
There are a number of other rain garden incentive programs available in communities across Puget Sound. We keep an updated list of incentive programs so homeowners can check if there is an incentive program in their area. Also, if you can rally a few of your neighbors to go in for a cluster of rain gardens, Stewardship Partners and Boeing Charitable Trust may be able to provide those rain gardens free of charge. You just need six to eight adjacent neighbors to beautify your street, control flooding and clean up water pollution!

Maintaining a rain garden

Not at all. Rain gardens can be designed to require very little maintenance by choosing the right plants, doing close-plant spacing, applying mulch, and quickly pulling the early weeds to prevent future maintenance problems. Some gardens require as little as 15 minutes of care a month during the warm season. You should add mulch every year to control weeds and replenish organic material in the soil. During the summer months, you should water every one to two weeks for the first year, and every two to four weeks for the second year. Rain gardens with native plants should require little to no watering after the first two or three years.*

About our campaign

Please check our latest rain garden workshop schedule at the Events page.
There are a number of rain gardens all over Puget Sound already! Check them out on our Google Map of Puget Sound rain gardens. Stewardship Partners has a number of previous rain gardens installations on our Picasa and Flickr sites. For more examples of rain gardens and other green infrastructure, visit our Pinterest and Houzz pages!

*Source: Washington State University’s Rain Garden Handbook for Western Washington.