Gravel Gardens are Finding a Home

(Editor’s note: Gravel gardens are popping up in public spaces from Scott Arboretum and Chanticleer Garden in Pennsylvania to midwestern corporate campuses. This is the first in a two-part series on the trend.)

by Nina A. Koziol

Down the road from my grandmother’s house in Essex, England, is the garden of the late Beth Chatto, a celebrated plantswoman. But unlike other perennial gardens in the English countryside, filled with delphiniums, clematis and roses, Chatto’s landscape featured a dry, gravel slope filled with drought-tolerant plants that thrive in the Mediterranean. In 1989, she described it in, The Green Tapestry: Choosing and Grouping the Best Perennial Plants. While most readers might picture England as rainy and overcast, Chatto gardened in an area where the annual rainfall averages 20 inches.

Fast forward. Landscape designer Cassian Schmidt is considered the guru at the forefront of the New German landscaping movement. Director of Hermannshof, the world-renowned research and botanic garden in Germany, he began replacing lawn with large areas of prairie-style plantings and gravel gardens, creating combinations of perennials and grasses that feature our midwestern native plants.

Today, gravel gardens are trending as a means to create low-maintenance, pollinator-attracting landscapes in many public gardens and corporate campuses. Roy Diblik of Northwind Perennial Farm in Burlington, Wisc., began his love affair with gravel gardens in 2007. “I went to Germany and saw Cassian Schmidt’s garden in Hermonshoff and I felt sorry for America because we don’t try things,” he said. “It was the coolest thing I’d ever seen and couldn’t wait to get home and try it. It’s about creating longevity and conserving costs.” Diblik has worked on several gravel gardens including the newest at Argonne National Laboratory in Lemont, Ill., which he calls the largest of its type in Illinois. “The building houses the world’s biggest computer and they have viewing windows where you can see the plants.”

Jeff Epping, director of horticulture at Olbrich Botanical Gardens in Madison, Wisc., and owner of Epping Design and Consulting LLC, has been designing gravel gardens since 2009 with inspiration from Diblik. “Roy and I have been great friends for a long time. I saw his gravel garden a year after he put it in and I thought, ‘What the heck is this?’ He said he didn’t know how it was going to work, but he’d seen one that Cassian did that was 20 years old. The first time I saw it, it was a sea of gravel but I thought, oh this is cool.”

Epping has worked on the largest gravel garden in the country at Epic Systems in Verona, Wisc., along with four gravel gardens at Olbrich and one at his home. “The biggest one at Olbrich is right at the front entrance.” The borders feature a beautiful mix of Russian sage, little bluestem, coreopsis, allium, coneflower, leadplant, prairie dropseed, asters and calamint among many others. The plants require little care and provide a stunning succession of blooms up to the fall frosts.

Planning and Planting

Unlike the raked layer of gravel found in Japanese-style gardens, the “new” gravel gardens are essentially a five-inch layer of angular-edged pea gravel like quartzite that sits atop soil. This allows the roots of the plants—especially native prairie plants that have deep roots—to travel down to the soil while preventing weed seeds from germinating in the top layer of stones. “We had to be careful when we prepped the beds,” Epping explained. “We excavated as deep as we could. If you have a gravel garden next to a walkway, it’s inevitable that whatever debris falls on the sidewalk will wash into the edge of the gravel garden. It’s interesting to see how much reseeding goes on at the edge. At home, my gravel garden runs along the street and our streets get sanded in the winter, so that sand goes into the gravel garden when the street is plowed.” The sand becomes a substrate, filling in spaces between the rocks and creating a growing environment that encourages seedlings. “I’m keeping an eye (continued on page 31)

The long roots of plant plugs reach through the gravel to the soil layer below

(continued from page 28) on that edge and this spring I noticed Echinacea pallida and Euphorbia seedlings.”

When planting, Epping sometimes uses plugs that are 2 1/2 inches with long roots. “It takes awhile for them to get up to full size, but they are placed closer together.” In 2009, he and Diblik laid out hundreds of plants for Olbrich’s Visitor’s Center garden. “I was still a little skeptical at first, but the third and fourth year it got better and better.” Today, visitors are awe-struck as they enter the garden.

Return on Investment

“For some years I had dreamt of making my Gravel Garden, with plants adapted to the prevailing conditions, instead of watching mown grass turn biscuit-brown for weeks every summer.” — Beth Chatto

The benefits of a gravel garden are many. There’s no annual mulching—putting down organic matter that would encourage weed seeds—or endless spraying or weeding. As a replacement for lawn, there’s no mowing or weekly irrigation.

“Corporate campuses get mowed 26 times a year and someone has to come in and fluff up the mulch in the beds,” Diblik said. Some estimates put gravel gardens at about 80 percent less work to maintain than a conventional garden with similar plants. The upfront costs are significantly more for the purchase of gravel and plants, and the preparation and planting, but over time with much less maintenance the costs are greatly reduced compared to traditional landscapes.

There’s also the winter interest. “Let the perennials stand for interest and winter hardiness,” Epping said. “Leaving the top growth and covering the crowns insulates them.” Epping removes the plant debris in spring at Olbrich and at home. The clippings are placed in two-foot mounds to release any overwintering beneficial insects and then moved to a compost pile. “We’re collecting the tops and taking them away so the plants are not getting the organic matter. However, if you talk to prairie experts and people who study soils, the root systems of plants are always growing and dying so there is some organic matter and microbes and life forms that inhabit the soil.”

Hold the fertilizer. “I haven’t found any need for it to be honest,” Epping said. “The soils in Olbrich are pretty decent agricultural-type soils. We’re dealing with plants that are used to very infertile soil—we never fertilize. Roy asked Cassien and he said there’s no need. In some of the better gravel gardens that are drier and more stressed, the plants just thrive. (continued on page 34)

(continued from page 31)

Not Your Grandma’s Lava Rock

Some readers will recall the wildly popular use of red or black lava rock in residential planting beds back in the 1980s. That’s not what today’s gravel garden is about. “I tell people that these gravel gardens are another good thing we can do for the environment,” Epping said. “The best place for one is in the lawn area, because lawns don’t support insects and a gravel garden will be lower maintenance. I don’t see anyone replacing every inch of their garden with gravel, but they can have little beds around the foundation of the house on the south or west sides.”

An Artful Pollinator Paradise

The gravel-prairie-style meadow gardens here and abroad are a seamless display of native midwestern plants, nativars and non-native, drought-tolerant plants. The design intent is not to replicate a natural plant habitat, like the Schulenberg Prairie at The Morton Arboretum in Lisle, but to create a palette of fascinating plants with a wild, four-season interest and pollinator-attracting potential.

Siting the Gravel Garden

Since most midwestern prairie plants require full sun and well-drained soil, a gravel garden in a sunny spot makes sense. Parking lot island beds are ideal situations since they are typically raised and contained with a concrete curb that corrals any gravel. In areas around corporate buildings that have poor drainage, a gravel garden can help capture and slow the water percolating into the ground. Epping cautions that when snow must be moved in the parking lot, it mustn’t get dumped onto gravel beds because it may have debris or soil in it.

Before the layer of gravel is placed, the soil can be amended if needed. That’s often the case where the soils are heavy dense clay. That wasn’t possible at Argonne when Diblik did the planting. “There were wires and pipes all over the place,” he said. The plants — typically plugs with deep roots — are placed closer

together than in a typical perennial garden. Care must be taken to avoid getting soil mixed into the gravel layer. Rakes and blowers are useful for removing organic matter that might get caught in the gravel.

Once a gravel garden has matured by year two and three, established plants are more drought tolerant. However, watering newly installed plants is crucial — and not just once. Frequent watering — two or three times a week —helps the plants get established. Epping said that daily watering might be needed for the first six or eight weeks.

After the initial planting, the site often looks like a sea of gravel dotted with small plants. By the second year, however, the gardens tend to look full and beautiful. “It can be designed and more floriferous using nativars to create a more designed look but one that’s very naturalistic,” Diblik said. “From a sustainability standpoint, it’s about low inputs and minimizing the use of fossil fuels. The gravel garden is an interface between the manicured and the completely natural.” More to come.

Bed-fellows include native cultivars and non-native plants such as coneflower, yarrow and butterfly weed.