These beautiful and environmentally friendly landscape additions have a place in wet and dry climates
Simply put, a rain garden is a sunken planting bed. Rain gardens are great home projects because they appeal to both our practical and idealogical selves. They benefit local wildlife and water bodies while also helping to improve drainage on properties.
With more municipalities tasking homeowners with managing their stormwater on-site, and more homeowners looking to incorporate plants that will attract birds, bees and butterflies, a rain garden is a landscape home run. Here’s what you need to know about adding one of these useful and attractive garden features.
Rain gardens, like all planting beds, can be beautiful additions to a landscape’s design. They can also help resolve drainage issues on your property and provide valuable environmental benefits to local wildlife and ecosystems. When you add a rain garden, you:
1. Add habitat. If you fill your rain garden with wetland plants native to your region, you can provide local wildlife with habitat, food and host plants. Additionally, it’s an opportunity to incorporate plant types you might not normally see in a home garden.
2. Keep runoff out of the stormwater system. By draining water on-site instead of directing it into the stormwater system, rain gardens keep pollutants out of our water bodies and replenish local aquifers. “Rain gardens use the natural filtration processes of soil and plants to purify stormwater runoff from streets, patios and rooftops,” says landscape designer Amy Whitworth of Plan-it Earth Design in Portland, Oregon. Rain gardens also take the strain off stormwater infrastructure and help reduce flooding and erosion that happen downstream.
Rain Garden 2: Creating Sustainable Landscapes, LLC, original photo on Houzz
3. Use a readily available supply of water that doesn’t tax the system. A rain garden is a planting bed that survives only on rainwater, except in extreme drought conditions — it doesn’t rely on water that has been cleaned, treated and processed. In southeast Michigan, where landscape contractor Drew Lathin lives, a 500-square-foot roof can shed 10,000 gallons of rainwater per year. Imagine directing that water to a planting bed instead of down the storm drain. “In our region, the only reason you wouldn’t [use that water] is the effort and the cost,” he says.
Rain gardens aren’t appropriate only in wet regions. “I know many places in the U.S. benefit from rain gardens: areas with regular rainfall throughout the year, like the Midwest, and drought-ridden areas that really need to recharge their underground aquifers, like Southern California,” Whitworth says. “Here in the Pacific Northwest, we get small amounts of rain all the time, so rain gardens work really well here to absorb most of our rains.”
Who to hire: A landscape designer, landscape architect or landscape contractor can help you add a rain garden as its own project or as part of an overall landscape plan. While it’s not the most complicated of landscape projects, Whitworth suggests looking for professionals who specialize in sustainable gardening practices, as they are more likely to have experience with this type.
DIY: It might not be necessary to hire a professional. “You can absolutely successfully design one yourself,” says Lathin, who has built over 40 rain gardens with his company, Creating Sustainable Landscapes. It might take a few weekends, some simple calculations and the help of a few friends to accomplish. “The first one that I built still works,” he says.
Cost range: The cost will depend on whether or not you hire a professional or do the project yourself, as the labor cost is the only real difference between adding this and adding a traditional planting bed. In addition to planting and mulching, the garden will need to be dug out and, in some cases, soil will need to be replaced and amendments added.
Expect to pay $3 to $5 per square foot to install one yourself, and $7 to $12 per square foot if you hire a professional. “It would cost two to four times more per square foot than a typical planting bed if you hired me,” Lathin says.
Rain Garden 3: Plan-it Earth Design, original photo on Houzz
Typical project length: A professional crew can accomplish the installation in about a day. If you do it yourself, it will take longer, as it’s a pretty physically demanding project.
Best time to start: Depending on where you live, fall or spring is the best time to plant your rain garden. “Fall is a good time to build one here in the Pacific Northwest, because the rains have started, making it easier to dig,” Whitworth says. “Plants are easiest to establish at this time of year as well, giving them three wet seasons for good root growth before our first season of drought, summer.”
It’s also possible to break up the process. “I’ve dug them in the fall and planted them in the spring,” Lathin says. He adds that in regions with wet, cold winters, it’s important not to plant too late in fall, as the water and the freeze-thaw cycle can lift and wash away young plants that haven’t developed strong root systems yet. “You should never use seeds for a rain garden, because rain will wash them away and leave bare spots for weeds,” he says.
How to Get Started
1. Decide where to put it and how big to make it. When deciding where to put your rain garden, consider how it will contribute to your landscape design as a whole.
Additionally, make sure it’s at least 10 feet away from the house, away from buried utility lines, in a part of the garden that can drain water — you don’t want water standing for more than a day or two — and where you can actually direct water to (this might mean piping water to the rain garden). “Be aware of where the rain garden will overflow, and make sure it will not affect your neighbors downhill from you or next door,” Whitworth says.
Rain Garden 4: Pennsylvania Landscape & Nursery Association, original photo on Houzz
The rain garden’s size will be determined by how much impervious surface will drain into it and what type of soil you have. You can have multiple rain gardens on your property, or you can just aim to capture some of the water that will be running off. “A small rain garden is better than no rain garden,” Lathin says.
2. Shape your rain garden. Once you have determined your rain garden’s size and location, it’s time to pick its shape. “A long, narrow one can work along an existing garden bed on a small property,” Whitworth says. She adds that for larger properties, you can choose a rounder shape, as long as there’s room for other garden functions.
Landscape architect Falon Mihalic of Falon Land Studio recommends using a nontoxic spray paint to mark the rain garden’s shape on the ground before you start digging, as shown here.
3. Choose plants. Selecting plants for a rain garden can be fun, as you will likely be working with species you might not otherwise get a chance to use. “They contain a variety of wetland plants that may have year-round interest, just like you’d design for any planting bed,” Whitworth says. Flowers, shrubs and even some trees can be planted in a rain garden. Rushes and sedges are popular evergreen additions.
While it’s not essential to use only native plants, they can be better adapted to the environment you’re creating and can offer better wildlife value.
4. Design a rain garden that complements your landscape. After you’ve selected the site, size, shape and the plants you want to incorporate into your rain garden, it’s important to design a garden that will complement the rest of your landscape, in terms of seasonal interest, layout and the garden’s evolution.
Rain Garden 5: Countryside Flower Shop and Nursery, original photo on Houzz
Maintenance: Aside from the weeding and watering needed to establish it, as is necessary with any planting bed, a rain garden is very low-maintenance, especially if you use native plants. “The biggest difference is making sure the basin doesn’t fill up with organic debris or excess mulch over the years — reducing water storage capacity — or that the inlet doesn’t get clogged with debris, especially if it is carrying water through an underground pipe into the rain garden’s basin,” Whitworth says.
Permitting: While rain gardens usually don’t require a permit, it’s always good to check with your local building department. “Here in the city of Portland, permits are generally not required unless the slope is greater than 10 percent and you are not in a landslide area. If your rain garden has an overflow drain that leads to the storm system, a permit may be required,” Whitworth says.
Depending on where you live, you’ll also want to check with your homeowners association, especially if you’re installing one in the front yard.
Rain Garden 6: Moody Graham, original photo on Houzz
More information: A rain garden is just one way you can manage stormwater on your property. One can be added on its own or in conjunction with other techniques, such as adding permeable paving, planting a green roof or swale, or installing a rainwater cistern.
If your landscape is not suitable for a rain garden, you can reduce stormwater runoff and improve soil health in many other ways. Whitworth suggests planting a tree, which helps reduce runoff and knits together hillside soils, or reviving soils with compost and beneficial microbes. “Do less cleanup on your property and let those autumn leaves go back into the soil,” she says. For leaves that don’t break down readily, such as oak and southern magnolia, run over them with a mulching mower.