Image Source: Creative Commons
In part one of this blog series, we explored the benefits of rain barrels and featured tips from rain barrel expert Matt Trokan for installing one in your outdoor space. In today’s blog, we’ll be looking at another way you can manage stormwater in your yard: rain gardens. We’ll look at the many ecological benefits of rain gardens and be featuring advice for installing you own rain garden from expert Owen Hunter-Linville of Groundwork Ohio River Valley.
To learn more about why managing rainwater is important, not only for our human neighbors, but also for local ecosystems, check out the first part of our “Rain Check” series.
What is a Rain Garden?
A rain garden is constructed by digging out a depression in the earth where native plants and grasses are planted. They are built to collect rainwater from impervious surfaces like roofs and streets. During a storm, water collects in a rain garden and is then filtered and cleaned by the soil and absorbed into the ground instead of running off into local waterways. To learn a little more about rain gardens, we talked to Owen Hunter-Linville, a Green Corps member at Groundwork Ohio River Valley. Owen has installed many rain gardens during his time with Groundwork. Check out Owen’s advice in the tips below:
What are the benefits of rain gardens?
- Reduces Runoff
The biggest benefit of rain gardens is that they do a great job reducing stormwater runoff. They need to be strategically planned and placed to ensure they are as efficient as possible, check out the location and installation section below for more tips on that. Rain gardens aren’t just for those of us with yards, they are also great additions to schools and businesses. Owen says that many of the rain gardens he installs with Groundwork are for schools and parks, usually for receiving stormwater runoff from parking lots. If you aren’t able to install a rain garden in your outdoor space, maybe you can advocate for one at a local park, school, or at work. They will reduce flooding and can be a great way for local organizations to make a significant impact to help the environment.
- Filters out pollutants
Rain gardens not only capture stormwater runoff, but they also help to filter the water, removing pollutants from the water. The Central Ohio Rain Garden Initiative explains the process well:
“Gardens remove and degrade contaminants through microbial processes, plant uptake, exposure to sunlight, and absorption to soil particles. Properly designed rain gardens capture the first inch of rainfall, and drain within a day. Since most storms produce less than one inch of rainfall, capturing it reduces pollutants significantly.”
- Welcomes Wildlife
Rain gardens are not only constructed as an area that can collect water, but also as a place where plants can thrive. In previous blogs, we’ve emphasized the importance of using native plants in our garden spaces and your rain garden is no exception. The fact that rain gardens are gardens means you can design them to look very beautiful. Rain gardens are a triple threat: they’re nice for you and your neighbors to look at, they attract local wildlife (especially pollinators), and they mitigate stormwater runoff issues.
General Installation Steps + Tips
Image Source: Franklin Soil and Water Conservation District
Step 1: Pick a good site
Site selection is key to an effective rain garden. To avoid cracking your foundation, Owen recommends a spot at least 7-10 feet from the base of a building. A location downhill from your downspout is the most ideal. If you have a flatter yard you’ll have to work a little harder to make sure the trench you dig to feed your rain garden slopes effectively.
Tip: to pick the best spot, Owen says to observe your yard while it’s raining. That way you can see how and where rain water generally moves in your space. Build your rain garden where water naturally runs in your yard.
Step 2: Percolation Testing
Before you start digging out your rain garden you need to make sure that water is able to soak into the ground. To do an infiltration test, you’ll dig a hole and fill it with water to see how long it takes for the water to be absorbed. Check out this video to learn how to do your own simple percolation test.
Step 3: Dig trench + garden
Owen says that to ensure that your rain garden collects as much runoff as possible you need to dig a channel from the base of a downspout to the garden. This channel will direct runoff from your roof to your rain garden. If you want your trench to be extra effective, you can line the bottom with a layer of plastic and put gravel on top.
The trench will run from your downspout to your rain garden.
To dig out your rain garden, you should mark the area and hammer stake around the perimeter. (Tip: make sure you call 811 before you dig — the Ohio Utilities Protection Service will mark any underground utilities for you to avoid while digging). Use a string level to confirm that everything is the same height. Rain gardens are generally 10-12 inches deep with gently sloping walls. This process is important and can get a bit complicated so we recommend checking out this video or reading this article to see how others have built their rain gardens.
Note on sizing your garden: Owen says that rain gardens can typically take water from an area 2-3 times larger than they are. To calculate the size that’s right for you, Owen recommends visiting the Three Rivers Rain Garden Alliance Calculator. It’s a great tool that takes into account things like soil type and slope of your yard.
Step 4: Choose your plants
In terms of planting, go for native flowering plants and wetland species. Owen recommends checking out this guide from the Warren County Soil & Water Conservation District for ideas of what to plant. Layering your planting and plants types will also be helpful. Put the obligate wetland species at the bottom of the garden and the facultative wetland species at the edges (you can search for which plants fit in those categories using the USDA’s Wetland Indicator Search tool).
- Mulch: Many people finish off their rain gardens by mulching around plants. Mulch can be a great way to make your rain garden look beautiful, but Owen recommends that people go for double shredded hardwood. Regular mulch floats and won’t last long.
- If you have heavy clay soil: Once you’ve dug your garden out but before you plant, Owen says you might want to till some compost into the top layer, this will help with water infiltration and uptake.
Luckily, rain gardens don’t come with too much ongoing maintenance. The main tip Owen had was to keep an eye out for invasives because they can take over quickly. He recommends weeding once every month of so. If it’s been a while since it rained, you might need to water the garden to keep the plants alive. In terms of winter maintenance, there’s no need to put the garden to bed or do much for the winter months, if you’re using native plantings then they will be prepared for the winter season.
- Slope: Getting the slopes right can be tough, especially from the downspout to the rain garden. Check out this tool from the Three Rivers Rain Garden Alliance for more information about determining your yard’s slope.
- String levels: String levels can be difficult to use, but it’s a very important tool for building an effective rain garden. Check out this article for tips on using a string level.
- Mosquitoes: As long as the ground can absorb the water collecting in your rain garden then mosquitoes shouldn’t be an issue. Check out the video in the installation section above to learn more about percolation tests.
- Keystone Flora
The experts at Keystone Flora can help you figure out which native plants are best for your rain garden. You can visit their website for more information. They are currently open by appointment only, to schedule an appointment or ask questions you can call (513) 961-2727 or email email@example.com
- Central Ohio Rain Garden Initiative (CORGI)
This organization is based in Columbus, but they have lots of resources for folks interested in building rain gardens throughout Ohio. Check out the resource section on their website for quick tips and thorough guides for building your rain garden.
More Welcoming Wildlife Resources
Urbanization and suburban sprawl has a big impact on the wildlife that have always called our cities home. Welcoming wildlife in the literal sense by doing things like planting native plants and feeding birds is great, but we should also be trying to make our outdoor spaces work with natural systems to support the ecosystem. By adding a rain garden to your outdoor space you are not only helping to curb stormwater issues for yourself and your neighbors, but you are also keeping polluted runoff out of local waterways and creating habitats for your wild neighbors.
We’d like to extend a big thank you to Owen for sharing so much great advice. If you’ve installed a rain garden in your outdoor space and have tips or ideas for others looking to do so, feel free to leave them in the comment section below. For more Welcoming Wildlife resources visit imagoearth.org/welcoming-wildlife. Imago has also created a Green at Home Facebook group that was designed as a place for people to ask questions and share resources for making sustainable changes in their daily lives. Feel free to join the group and ask questions about rain barrels and gardens or anything else sustainability related.