FOCUS: Stormwater Management Techniques Landscape Awash? Your company should employ rain gardens

By Nina Koziol The record rainfall this past May left many homes and streets with standing water. Designing a rain garden is often an effective way to capture some of the excess water on a residential client’s site.

Flooding is a problem not only in the Chicago metro area, but in places throughout the state. “Potential clients are everywhere,” says Carol Becker, owner of Sage Advice Landscape Design and Consulting in Park Ridge, Illinois. “Clients may live close to rivers or where housing has been built where there was no consideration for drainage. They can be in communities where they allow houses to be built almost to the lot lines.” And, that means less permeable space for water to enter the ground.

A one-inch rainfall on an acre produces about 27,000

gallons of water. Some of it runs off onto beds, borders and grass, but that’s problematic, too. “Lawn really is impervious because the roots are only 3 to 4 inches deep,” said Grace Koehler, sales manager at Pizzo Native Plant Nursery. “It will eventually permeate the soil, but when it’s dry, the water runs right off the lawn.” In its most basic form, a rain garden is a depression in the ground that’s filled with sand, topsoil and compost and planted with native perennials, non-natives and grasses with deep roots that let water slowly permeate the ground. Besides addressing flooding, putting water back into the soil helps to recharge underground aquifers and reduces (continued on page 12)

(continued from page 10) surface runoff (and pollutants) to streams and rivers.

The rain garden concept is sometimes misunderstood. “A rain garden is kind of a low spot in the ground where water can gather and infiltrate,” said Trish Beckjord, Fox River Initiative program manager at The Conservation Foundation. “Typically, it’s water collected off a portion of the roof that will soak into the ground within 24 hours—it’s not a place that’s always moist. If that was the case, instead of a rain garden, we’d be looking at a garden of moisture-loving native plants.”

Sustainable vs. Scruffy The rain garden philosophy—create a landscaped

basin where rainwater runoff can gently seep back into the earth instead of into a basement, garage, or sewer—is noble, but a common complaint is that rain gardens seem untidy.

“If they look weedy or messy, the right plants haven’t been chosen for the site,” Koehler said. “You don’t have to use all natives but you should give consideration to the type of plants. Some are rhizomatous and form large mats and should only be used in large landscapes.”

Marcus de la Fleur acknowledged the challenge in his presentation at ILCA’s 2018 Impact Conference. “Rain gardens are notoriously difficult to design—they can be a little too dry or too wet and the plants don’t (continued on page 14)

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(continued from page 12) want to grow,” he said. Determining where and how the water flows on the property and the quality of soil are the first steps.

Design a rain garden as you would any other perennial border. Select plants based on their ornamental qualities—flower and foliage color, form, texture and seasonal interest—and plant them in drifts. It has to look intentionally designed—it’s not necessarily meant to look like a natural area, unless that’s what your client wants. In many cases, clients have traditional landscaping, but with a drainage problem. Unless they are expecting something wild and informal, you’ll want to create a design that works with the rest of their property. Edging a rain garden with boulders, permeable pavers or gravel will help define the space and neatly separate it from the lawn.

Plant Selection Rain gardens can be placed just about anywhere—sun or shade—as long as you choose the appropriate plants. “The garden can be any size,” Koehler said. “When you think about detention or retention areas, they’re really just large rain gardens.”

Beckjord’s home rain garden is a low area that receives water from the roof. “I have a channel that’s paver-lined from

the downspout,” she said. “From July through September it’s very dry if there’s no rain. The best plants are probably mesic-prairie plants. It’s a native plant that can take some inundation for 24 hours and a broad spectrum of natives can take that.” Mesic soils are medium moist and comparable to average garden soil while wet-mesic soils are medium moist to soggy most of the year.

Herbaceous native plants that can handle moist sites in sun include swamp milkweed, common tussock sedge, blue flag iris, rosin weed, spiderwort, switch grass, Joe Pye weed and cup plant. A big mistake, Koehler said, is choosing wetland plants for all rain gardens. “Each site is different and every soil is different and that’s why we don’t give plant lists.” (See the online resource list below for more information on designs, plants and suppliers.)

Shady Sites Many of Becker’s projects in flood-prone Park Ridge are in shade. “I’ve used native shrubs, like bottlebrush buckeye, and native sedges,” Becker said. “There are many sedges that are beautiful but not very showy. It depends on the client.” Sedges can form the matrix of the planting or they can be used on the edges or in groupings. (continued on page 16)

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Designing a rain garden for full or part shade is a matter of picking the right plants. “Common mountain mint is in a light-shade rain garden at Midwest Ground Covers,” Beckjord said. Longbeaked sedge (Carex sprengelii), pretty sedge (C. woodii) and brown fox sedge (C. vulpinoidea) are some of the native sedges that perform in moist woodlands. Canadian anemone, green dragon, jackin-the-pulpit, Virginia bluebells, false and smooth Solomon’s seal and marsh marigolds are some native woodland perennials that can handle wet-mesic soil. Other native shrubs that tolerate shady floodplain conditions include paw paw, smooth hydrangea (Hydrangea arborescens), red-twig dowood, button bush, spicebush and nannyberry (Viburnum lentago).

Training gardens as it is with perennial borders. “Mulch is not needed and you plant the plants closer together, which minimizes weeding,” Beckjord said. She recommends cutting plants back in spring and leaving some stems standing six inches tall for native bees that will lay their eggs in them. “You can leave the debris on site. The way to do that is to chop it up so fine that it breaks down.”

“In the client’s defense, most garden crews don’t know how to take care of rain gardens,” Becker said. “They’re used to using mulch to cover empty spaces.” When Becker designs a rain garden, she placed plants closely together. “We do over-plant by traditional standards. In a native garden, there are so many plants there are few weeds.” She recommends using a triangular Dutch hoe to quickly remove weeds from between the plants as they establish the first season.

Beckjord says there’s an opportunity for landscape companies that offer maintenance. “We need to provide the expertise—how to manage a garden with native plants. It’s a market niche that’s Maintenance is just as critical with rain

The begining of a large rain garden project in Blue Island begging to be filled.”

Managing Client Expectations A picture (or drawing) is worth a thousand words. Rain gardens don’t look like the typical sunny perennial border or shade gardens. “People see rain gardens in pictures, but the plantings are often three to five years old,” Becker said. One client who asked for natives contacted her this spring to say that two-thirds of the plants didn’t make it, but they were likely warm-season species. “The plants weren’t up yet. I got her to be patient and they came up, but they are small.” Over-planting with plugs, or if the budget permits, one-gallon pots, will speed up the garden’s progress. Explaining what the garden will look like in year two can help avoid disappointment.

While many clients want carefree gardens, Koehler has a word of caution. “There’s no such thing as a maintenancefree landscape. It’s like any other perennial garden—it still needs maintenance and you need to manage invasive species.” Propose spring and fall maintenance in the bid.

Marketing Rain Gardens There’s a value in offering rain gardens to homeowners, especially those interested in butterflies, bees, birds and sustainability. “Rain gardens are really important solutions that landscapers can

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(continued from page 16) offer their client especially in dense, highly populated areas,” Koehler said. “Many native herbaceous perennials provide a lot of pollen and they’re also very specific host plants for moths and native bees.”

“We’re successful at selling rain gardens because they manage the water that comes into the yard,” Becker said. “But they’re also supporting nature— plants that filter water and return it to ground water and not an overloaded sewer system.”

“It’s a design tool, but it’s an important way to bring sustainable practices to our landscapes,” Beckjord said. “Being more sustainable includes using more native plants that are not only adapted to our region but that don’t require a lot of supplemental irrigation or fertilization to keep them looking good. Rainwater is a resource, not a waste product.”

Photo Right: The Blue Island Green Infrastructure Project created parkway plantings for stormwater management.

Photo Bottom: One of Blue Island’s parkway rain gardens. See more at https://www.nativelc.com/mwrd-blue-island

Online Rain Garden Resources

ILCA’s Sustainable Landscape Resources: https://www.ilca.net/ sustainable-landscaping/

Illinois Department of Natural Resources: Rain Garden Requirements and Plant Lists https://www.dnr.illinois.gov/education/pages/plantlistraingarden.aspx

Chicago Botanic Garden: Rain Gardens—Eco-Friendly Storm Absorbers https://www.chicagobotanic.org/conservation/rain_garden

Midwest Groundcovers: Rain Garden Plant List https://www.midwestgroundcovers.com/page/Rain-Garden-List

University of Illinois: Rain Gardens: Designs, Plant Lists & Suppliers https://guides.library.illinois.edu/c.php?g=347854&p=2345331

Community Collaborative Rain, Hail and Snow Network (CoCoRaHS Data) https://cocorahs.org

http://www.raingardennetwork.com/

http://dnr.wi.gov/topic/Stormwater/raingarden/

http://www.missouribotanicalgarden.org/sustainability/sustainability/sustainable-living/at-home/rainscaping-guide/

The Pizzo Group Native Plants. https://pizzogroup.com

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