Rock Solid

Gravel gardens offer attractive plants, lower maintenance and sustainability

Editor’s note: Last month we looked at gravel gardens in Wisconsin. We head back to Illinois for another look at this unique, trend-setting design.

by Nina A. Koziol

Tucked in a quiet, sleepy section of

Lemont, Illinois, sits the most powerful, advanced Cray supercomputer in North America. Argonne National Laboratory houses this scientific and engineering powerhouse that is used to research earthquake seismic activity, aerospace turbulence and shock-waves, advanced cancer treatment, national energy security, physical genomics and much more. It’s not only stateof-the-art, it’s propelling science into the future at an incredible speed.

It makes sense then that the landscape design for the computer facility is not only forward-thinking but sustainable. Or, perhaps it’s a nod to the Stone Age. After all, it’s a gravel garden. And right now, it’s the largest one in the state.

Designed by David Yocca, senior Landscape Architect/Ecological Planner with Solutions in the Land in Grand Rapids, Michigan, with planting design by Roy Diblik of Northwind Perennial Farm in Burlington, Wisconsin, the landscape plan began two years ago. Planting was done in August 2021 so the plants were only 11 months old when the photos here were taken. Diblik was thrilled to see how great the plants looked when he visited the site this past July to do additional planting.

“We had great design help from Austin Eischeid and the lead landscape architect David Yocca. It’s put on a lot of growth in just three weeks.” Atrium Landscape in Lemont does the maintenance. Diblik is adamant that plants not be dead-headed. “You want those seed heads standing here for interest. This is not a high-maintenance garden. You don’t need to touch anything.” The landscape is cut back in spring and debris removed then and throughout the growing season as needed. That type of maintenance is a far cry from weekly mowing.

The plants include natives: nativars and non-native pollinator-attracting perennials. Rudbeckia, yarrow, coreopsis, pale- purple coneflower (Echinacea pallida), goldenrod (Solidago rigida), feather reed grass, stachys, penstemon, allium, asters (including Twilight and Lady in Black), autumn moor grass (Seslaria autumnalis) and native grasses. There are evergreens — pines, spruces and creeping junipers — for winter interest. Some of the perennials are native to Illinois prairies, including a few that grow in gravel prairies, an extremely rare habitat found in only a few locations. “The new gravel garden replaced the seeded prairie,” Diblik said. “The prairie was overgrown with weedy stuff.” And that made it just a bit too wild-looking for the building manager. The one-year-old gravel garden is lower maintenance than the prairie and has more design intent giving it more of a garden feeling. Plugs were placed in drifts to make the design more legible. Some spots are planted as a fescue meadow, another low-input design approach. “The prairie had a lot of weedy plants,” Yocca said. “The gravel garden creates a more designed look, but one that’s very naturalistic. It’s the interface between manicured and completely natural.” One of the things he did was pull the views from indoors and from the outdoor seating areas into the surrounding landscape. “We’ve created little nooks. People ride their bikes around the campus here, and there are little seating nooks where they can meet, gather and work outside.” Several seating areas look onto the gravel garden where (continued on page 17)

(continued from page 14) butterflies and bees constantly work the flowers in summer.

Most of the plants are thriving since planting last year, but a few didn’t make it. “Watering is crucial the first few months after planting to get the roots established. And, the gravel has to be five inches deep,” Diblik explained. That depth allows the roots to reach into the soil below the gravel layer but at the same time it prevents weeds from taking hold because there is little organic matter in the spaces between the gravel.

Containing the planting beds with a barrier is important. Concrete curbs hold most of the gravel in place in the parking lot beds, but where they are not present, gravel is subject to snow plows and can be tossed onto the road. Debris from plows can be pushed up into the beds adding unwanted organic matter that would encourage weed seeds to sprout. Bioswales and Boulders

A slope of outcropping stone, boulders and cobbles receives runoff from the building. Underneath, thousands of feet of cables and other utility lines run from the building under the boulder “river” so great care was taken when excavating. “The boulders imply water without water,” Yocca said. “They evoke a sense of water and of the flats and discharge zones at nearby Waterfall Glen.” Discharge is captured by nearby bioswales.

A big challenge was the large concrete facade that screens the service dock. Yocca secured Virginia creeper vines to the wall using a special tape rather than drilling into the wall. The vines will supply fruit for birds and offer a beautiful red fall color. “It’s a work in progress,” he said.

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Poplar Grove, IL

21283 IL Route 76 Poplar Grove, IL 61065

Clinton, WI

11228 East County Road X

Lorem Clinton, WI 53525 Salem, WI 7530 288th Avenue Salem, WI 53168 1-262-537-3326

ipsum wholesale@breezyhillnursery.com

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Selling the Idea

The Argonne site is surrounded by hundreds of acres of forest preserve. There are 500 acres of woodlands, 330 acres of grassland and prairie, 50 acres of wetlands and other habitats. Pine trees on the site were planted in the 1950s to improve habitat and advance forest succession. Ecosystems today have grown in and around research buildings, enhancing the overall work experience.

“From a sustainability standpoint, it’s about low input, minimizing the use of fossil fuels,” Yocca said. Comparing the cost of a typical corporate landscape with acres of turf that must be maintained (continued on page 22)

(continued from page 20) throughout the growing season to a gravel garden with perennials can persuade the site managers to consider converting some of the lawn. “That’s how we got non-traditional corporate landscapes to change. We did a cost projection. Prairie versus turf and 26 mowings a year. It definitely takes an owner who sees the value and there are plenty of them,” Yocca said. “When they start to monetize the cost of maintenance, that’s a factor.”

Diblik sees another advantage. “You can see it’s a work in progress. But, they’re bringing researchers and politicians from all over the country who see the gravel garden,” Diblik said. He encourages landscape firms to market this type of landscape, but not only for sustainability reasons. “It’s wholesome,” he said. “There’s more evidence that people are healthier when they have a place like this.”