Up on the rooftop: Bernheim gardening to new heights

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By Stephen Thomas

CLERMONT -- Bernheim Arboretum and Research Forest aims high at being a regional pioneer in the field of horticultural science.


One might say they’ve aimed just above the ceiling.

Bernheim revealed the Living Roof Project, an ongoing research project testing various plant and soil samples for use on rooftops of area buildings. The project is being funded through the Brown Foreman Corporation.

Education director Claude Stephens said the project idea came from the creation of Bernheim’s new Visitor Center, the state’s first certified “green” structure, which implemented a green, or living, roof.

The living roof contains a soil foundation capable of growing plants on top of a building’s existing roof structure. The idea is to increase structure insulation, allow for better storm water drainage and protect the roof. A living roof could also become a source of plant and vegetable growth.

“It’s gardening on the roof,” said Bernheim horticultural director Dena Rae Garvue. “It acts as insulation, as a wildlife habitat, helps storm water runoff, plus it’s aesthetically beautiful.”

Garvue leads a team of horticultural technicians working on the Living Roof project including Eric Garris, Toni Hattier, James Moody and Alison Wheatley. The technicians began the project with 13 makeshift research beds, wooden platforms measuring 12 x 12 feet. Four plant groups and three artificial soil mixes are being tested.

Stephens identified the plant groups as rock garden plants, native grasses, Sedum’s and Kentucky glades, a plant unique to the surrounding region.

“Glades have never been common,” said Stephens. “They are small and found on limestone croppings. They grow in shallow soil and low moisture, which is exactly what you have on a roof.”

Once soils and plants are in place, the horticultural team will moderate changes over a three to five year period, noting which plants and soils work best and which may not work as well.

“We want to select as many types of plants as possible,” said Garvue. “We’re just launching the project. We may try other plants in the future, maybe vegetables and herbs. We want people to understand the variable importance of green roofs.”

Garvue said the green roof idea was more common in Europe and China. The Lady Bird Johnson Wildlife Center, located at the University of Texas, implemented a study program using native plants.

Garvue said test beds would remain open to the elements, a ‘full sun’ test, as if they were located on the tops of buildings.

“We could do various environmental conditions,” she said. “We have lots of opportunity to grow.”

Stephens said green roofs were possible on any buildings structurally designed to hold the weight. He said green roofs could be added to existing buildings depending on the structure’s strength.

“With this project we hope to figure out a way to see more of this,” Stephens said. “We want to expand this, be more experimental, bring more sustainability and feasibility to the design community.”

Garvue said a green roof would be economically feasible for homeowners as far as financial savings and possibly growing foods in a space-saving way.

“It would be more expensive initially, but over the long run you’ll get the benefits,” she said.

One of Bernheim’s test beds is located next to the Visitor Center. The rest are set up near the greenhouse across the road from the Visitor Center. Bernheim director Dr. Mark Wourms said the project was designed to allow public viewing during the ongoing progress. Each test bed is viewable at ground level.

“The public can see the progression and we want people to see this,” said Wourms. “Kids and adults can have their minds stimulated. They learn what a roof can do for us and for our environment.”

Wourms mentioned that the addition of local plant media, such as the glades, made the project environmentally important for the future of green roof projects in the local area.

“We want to do it right, and we may find plants that excel,” he said. “That would be an important contribution to the study.”

Garvue said the Living Roof project was a great educational tool. She said schools could easily create similar experiments for students.

“It’s a really nice mix of science and education,” she said. “There’s many new opportunities.”

Overall, green roofs are designed as an attempt to help fight global change and aid in water conservation. Wourms added that green roofs are better to look at than today’s common roofs.

“They’re actually really strikingly beautiful,” he said.