Rain Garden How-To
Get some helpful, expert tips on how to to add an earth-friendly rain garden to your yard.
The first rain gardens I ever saw looked a little clunky and out of place, a landscaping afterthought in an otherwise well-designed yard. That was easily a decade ago, and since then modern rain garden design has made huge strides. Today’s rain gardens form a green landscape that’s low maintenance and as beautiful as you want it to be. This beauty is more than skin deep, because rain gardens protect local waterways, groundwater supplies and city sewer systems by slowing storm runoff and filtering pollutants.
Rain gardens also help your budget in several ways. When you replace turf with a rain garden, you immediately save time and money on lawn care. In many regions, you can earn rebates from local water boards or utilities for installing a rain garden. Some municipalities require homeowners to reduce their property’s storm water runoff—or pay higher storm sewage fees. A rain garden treats runoff in a way that’s eye-pleasing and easy to maintain.
Wondering if a rain garden is right for you? Glean some in-the-know tips and check out a few rain garden designs from David Hymel and Marilyn Jacobs, owners of Rain Dog Designs in Gig Harbor, Washington.
Call 811 Before You Dig
Every landscape project—including installing a rain garden—begins with locating underground utility lines.” All jurisdictions require some notification,” says Hymel. “If you dig and hit a line, you could wind up paying costs for utility repairs, first responders and fines for disrupting utility service.” When utility lines conflict with where you hope to put a rain garden, simply shift the location. “This can be a challenge in a small yard, but there are always options,” Hymel says.
Team Up With Neighbors
Consider working with neighbors to share resources and reduce costs. “When neighbors coordinate installing rain gardens, they can save as much as 30 to 35 percent on construction costs, such as hiring a single excavator to do the digging,” Hymel says. “We coined the phrase ‘neighbor labor’ to describe this process, which ultimately creates community.” This entry rain garden is part of a 2009 community project in Puyallup, Washington that featured seven rain gardens on one block.
“Neighbor labor helps homeowners with even no garden experience succeed,” Jacobs says. “We encourage neighbors to work together to plant and maintain rain gardens. Neighbors can tackle weeding or mulching rain gardens together and have a barbecue after. It’s a good option for developing community.”
Sharing Plants Builds Community
Sharing plants is another aspect of rain garden neighbor labor. “When plants do well for one person, they can easily share those plants with neighbors,” Jacobs says. In this small front yard rain garden, ornamental grasses and ground cover are thriving and could be divided to share starts with neighbors.
Think About Extra Soil
To create a rain garden, you need to dig an 18- to 24-inch-deep basin that catches and holds water. Consider what you’ll do with the soil that’s generated as the hole is dug. “Sometimes soil can be incorporated into berms around the rain garden or into other landscaping in your yard,” Hymel says. “Or you might need to haul it away.” This rain garden includes berms along the edges.
Rain Garden With Berms
Once planted, the berms form a natural-looking setting. The central depression catches and retains rain water. A typical rain garden like this can easily generate five cubic yards of soil. Because that’s a large amount of soil to move, it’s a good idea to hire the right equipment to make the job easier. The gravel areas help water enter and exit the rain garden easily without eroding soil.
Before Installing a Rain Garden
Knowing when you need to hire professionals to help with installing a rain garden depends, in part, on how large the job is. If you plan to renovate a traditional lawn and plantings, like this one, to create a low-maintenance, low-water use landscape, a garden designer with rain garden experience can help conceptualize the new earth-friendly design.
After Installing a Rain Garden
The new front yard design features a green landscape with no water-guzzling lawn, island planting beds and a rain garden to capture storm runoff from the roof. Hymel suggests that for rain garden designs that are smaller than this type of whole yard makeover, a contractor can still be helpful. Consider hiring a contractor to tackle soil excavation and/or a designer to help with plant selection and placement.
Rain Garden on a Slope
When building a rain garden on a slope, instead of excavating one long and extremely deep channel, create a terraced garden with multiple cells to hold and retain water. Hymel suggests staging the cells in a design that’s eye pleasing. A straight line, like this, works when space is at a premium. For larger areas, arrange cells in a serpentine fashion.
Keep the Trees
It’s possible to incorporate existing trees into rain garden landscapes. Best success occurs with smaller trees (roughly 1- to 1.5-inch caliper). Why? “Because big trees tend to be water hogs,” says Jacobs. “With larger trees, rain garden plants have a tougher time establishing, because tree roots gobble available moisture.”
Choose Plants You Love
Rain gardens can host a variety of plants to suit all kinds of garden styles. This front yard rain garden stages a colorful cottage garden. Jacobs suggests checking with your master gardeners local extension office for sample rain garden planting plans. “Using a plan can help you avoid a common and costly mistake: overplanting,” she says. “With overplanting, taller plants crowd out and can shade out lower ones.”
Make It Fit
Rain garden shape options are limitless. You can design a rain garden to fit any part of your yard. This homeowner transformed a grassy lawn into a truly green landscape with a double rain garden flanking an earth-friendly permeable walk.
Curved edges give a rain garden a natural appearance. Hymel recommends using a garden hose to define the rain garden outline. Live with the design a few days, observing how it relates to the rest of your landscape, as well as interior spaces. Define the final outline with marking paint to make excavation easier.
Keep Weeds Down
Prior to planting, Rain Dog Designs relies on burlap coffee bags to suppress weeds. “In our region, we typically prep rain gardens during summer and plant in time for the fall rainy season,” says Hymel. “Plants in fall-planted rain gardens burst out of the ground in spring.” Jacobs advises buying plants in spring, when selection is best. “We nurse plants through summer by storing them in kiddie swimming pools,” she says.
Newly Planted Rain Garden
Help new rain garden plantings succeed by watering them for the first two growing seasons, until plants are well established.
Established Rain Garden
This is the same rain garden, two growing seasons later. Once plantings are established, rain gardens rarely need additional water, except during unusual drought periods. Rainfall usually provides the necessary irrigation.
Edging Lends a Finished Look
Adding a formal edging to a rain garden helps set it apart from surrounding lawn or landscape. A block edging favors a more formal ambience. To keep your rain garden low maintenance, choose an edging that can be easily mowed around, Hymel suggests.
Add a Rain Barrel
“In the Puget Sound area of Western Washington, installing a rain barrel or tank between downspouts and a rain garden can reduce the size of the garden by as much as 75 percent,” Hymel says. Reductions vary in other regions, but this technique makes it possible to include a rain garden in even the smallest yard—or parking lot (shown). Save more space by selecting rain water harvest tanks with building-hugging profiles (shown) and a smaller footprint than traditional rain barrels.
Options for Compacted Soil
Heavy clay soils that don’t drain can still host a rain garden. Hymel suggests adding an underdrain to transport rain water away from the rain garden planting area. The underdrain is essentially a perforated pipe covered with landscape cloth and surrounded by gravel. When water enters the pipe, it travels easily through impenetrable soils to a safe dispersion area like a storm drain or gravel dry well.