As rain events have become more intense and more frequent, you may have noticed stormwater from the street flooding your property, rainwater from downspouts carving gulleys into your yard, or a wet patch that never seems to dry out. All of these issues can be addressed with plants.
Jeff Lorenz, the founder of Refugia Design in Philadelphia, is known for designing immersive, native landscapes, but he’s also developed something of a knack for creating gardens that effectively manage stormwater. Refugia’s style is naturally well-suited to the task: The native plants that they work with are good at Lorenz’s three rules of stormwater management:
- Slow down stormwater, allowing the ground to absorb the initial surge.
- Spread the flow of water across the surface.
- Soak water back into the aquifer with the help of deep-rooted vegetation.
Plus, planting densely, as Refugia does, is a stormwater management trick in its own right. “Rain gardens seem complicated, and sometimes they are for good reason, especially in larger applications, but for most residential settings, just creating larger, more vegetated planning beds has a great impact on stormwater issues,” says Lorenz.
Below, he offers tips on how to have leverage your garden to help with stormwater management.
Photography by Kayla Fell, courtesy of Refugia Design.
Reduce your lawn and increase your beds.
“Reducing your lawn has a massive impact on stormwater,” says Lorenz. “We call it green concrete because it has very little absorption quality.” Consider expanding garden beds. Fall is a great time to plan for this, as you can pile up leaves on the part of the lawn you plan to turn into new beds come spring (see Why (and How to) Leave the Leaves). Two places Lorenze says you should definitely consider expanding your beds are where downspouts flow out, and anywhere your border beds are close to a low, wet point in the lawn. “Bring your garden bed out to incorporate that low point.”
Rethink how your care for your lawn.
For the lawn you do keep, consider tweaking your care routine. Let the grass grow higher and mow less often. “If you have a thicker, taller vegetation above ground, that’s going to help slow stormwater down,” says Lorenz. When it’s time to reseed, consider reseeding with fine fescues (and gradually transitioning the whole lawn), or if you’re open to a bigger change, replacing the turf with a full fescue or sedge lawn. Lorenze notes that in trials at the Mt. Cuba Center wood’s sedge (Carex woodii) was the best performing sedge lawn alternative for the Mid-Atlantic that can tolerate moderate traffic. (For more on this grass-like perennial, see Trend Alert: A Carex for Every Garden.)
Your irrigation might also need some rejiggering. “We discover a lot of properties that are always at a point of saturation because they’ve got these robust sprinkler systems that are keeping the ground wet,” says Lorenz. The ground loses its ability to absorb water in an actual storm, if it’s already saturated, but if it has the chance to dry out a bit and it has more absorbing capability. Dialing back your watering schedule will also have a positive impact by reducing the water your yard consumes. The ultimate goal is not to irrigate at all, says Lorenz, “We aim to make irrigation systems redundant, by using plants resilient in your area, that don’t require long-term coddling.”
Seek out native, resilient plants.
Putting plants in the path of stormwater or the place where the water gathers is key, but make sure they can handle both wet and dry periods. “You’ll water them the same as you would any other planting bed you’re trying to establish, but then the idea is that the plants can handle periods of dryness—even drought—and being kind of flooded,” says Lorenz, who notes that many grasses fit the bill. The best plants are going to be plants indigenous to your particular region, and a native plant nursery will be able to help you identify what will work best in your environment.
If you’re looking for plants to soak up rain in shadier areas, Lorenz suggests asking your nursery about different sedges (carexes) that will thrive in your area. “Carexes might not produce a root system quite as deep as switchgrass, but they will help slow water down and soak it up,” he says; for example, Pennsylvania sedge (Carex stricta, pensylvanica) and fox sedge (Carex vulpinoidea) produce root systems from 12 to 24-inches deep. Also consider adding to your shrub and understory layer. In the mid-Atlantic where Lorenz works, he uses white meadow sweet (Spirea alba), native smooth hydrangea (Hydrangea arborescens), and viburnums as well as small understory trees like dogwoods, including red twig dogwood or silky dogwood, and witch hazel.
Beef up your plantings.
“Densely-planted foundation and border plantings are a great way to start slowing water down,” says Lorez. This is especially true if you have a lot of water coming off your roof and the downspouts pass through your beds. Tip: If you have water getting in your basement, make sure that the beds around the house are pitching away from the house one or two degrees.
Companion plant for better water absorption.
“One of the key things that we look at is a diversity of root systems,” says Lorenz. In a forest, you’d find deep tree roots and lots of plants with surface roots in the herbaceous understory. As an example of a simple combination, Lorenz points to irises, which are great at slowing water down, paired with switchgrass, whose deep root system helps create a pathway for water to go back down towards the aquifer. One note: Do not plant deep-rooted plants near dry wells or septic systems.
Add this stormwater superstar.
One plant appears in almost all of Refugia’s rain gardens and mini bioswales: Switchgrass (Panicum virgatum). This perennial grass is native in much of the United States and Canada. Its root systems can be three times the size of the aboveground plant, and not only can it help water soak in, it can help filter petroleum-based pollutants out of the water if you plant it where it will catch un-off from your driveway or the street.
Reclaim your soggy spots.
If you’ve got a spot on your lawn that collects water every time it rains, you can use that area to your advantage and make a mini rain garden. “You might even want to articulate the grading a little, dig it out a bit more, and then vegetate it,” says Lorenz. Plants in the center of the rain garden need to be able to be happy with wet feet for a few days and also okay with periods of dry. Plants that fit the bill include many grasses, Joe Pye weeds (Eupatorium spp.), and irises like blue flag and dwarf crested iris (Iris cristata). Use the dirt you’ve excavated to create a gentle berm around the perimeter to help direct the water where you want it to go and avoid overflow in the depression. “We usually just use the excess soil and some stone from the dig, and then plant them so that they have root stabilization,” says Lorenz.
Work with the flow.
Water finds the path of least resistance, and you can often see evidence of where it naturally wants to flow. If you have a place where a gully has formed, Lorenz suggests creatively putting some stones and plants into the path of where the water flows; this could be a decorative arrangement of small and medium-sized stones right at the end of a downspout or boulder-sized rocks and shrubs in the path of an overflowing street drain. “In the mountains or forests you’ll see an ephemeral stream where you can tell that water flows from time to time, but it is dried out,” says Lorenz. “You’re just making a little naturalistic feature out of it.” Tip: If water flows so intensely that you’re afraid your new plants will be swept away, Lorenz says you can use sod pins or stakes to help them get established.
Filter the road water.
If water flows off the street or your driveway, you might consider planting a “filter strip,” which is planted along the sloped areas commonly found alongside roads, or even a mini bioswale, which is intentionally dug out to hold and direct water. “They’re meant to catch an initial stormwater rush and hold it to soak back into the ground or guide it somewhere where there’s maybe a larger catchment point,” says Lorenz. The vegetation can even have the capability to pull toxins out of that stormwater before soaking back in.
Engage your neighbor.
As you make changes on your property, share your efforts with your neighbors, especially anyone who is in the same path of stormwater. “As these superstorms keep coming in, you’re not going to have a perfect answer,” but the best solution is when a whole neighborhood works together, he says. “When it’s not just one property but multiple properties, that’s when you start to make an impact.”
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