Cooler weather will soon greet the assortment of greenery atop building A of Texas A&M’s Langford Architecture Center as Bruce Dvorak, assistant professor of landscape architecture, continues a research project to learn what plants will thrive on green roofs and green walls in Texas’ often hostile climate.
Green roofs and green walls promise many benefits, including lowering a building’s energy use, cleansing stormwater and improving air quality as well as providing aesthetic benefits and higher property values.
Since the project began in 2012, Dvorak said he has identified more than a dozen module-planted species that have done well on the Langford roof.
However, finding plants that will thrive in a green wall setting has been more of a challenge; none of the plants in the green wall portion of the project survived the cold 2013-14 winter.
A successful green wall hasn’t yet been planted in Texas, said Dvorak.
“There might be only certain types of plants that will grow on living walls in Texas,” he said. “Some plants have fibrous roots, some plants have bulbs — different forms of plants have different adaptability to living walls. Also, there’s so much variability in the design of a living wall — the challenge is to find plants that will work with a particular design.”
“There’s no book titled ‘Green Roof Species for Texas,’” said Dvorak, glancing at a bookshelf in his office. “We’re writing the book right now by finding out what will grow and what won’t.”
Graduate and undergraduate landscape architecture, horticulture and meterology students, who are documenting their project involvement in a blog, wrapped up the spring 2014 semester planting yarrow, climbing fig ivy, artemisia powis castle, sedge, rosemary and thyme, on roof modules and three green walls, on which they installed frames and irrigation systems. Each wall has a different design in an effort to learn which plants will work best with each respective design.
In the fall 2014 semester, they planted strawberries, mint, lettuce, kale and other vegetables on the roof and the wall while experimenting with different watering approaches. Dvorak plans to try still more varieties of plants in spring 2015.
Jose Franco, a Ph.D agroecology and sustainable food systems student, oversees construction and monitoring of the project.
“So far we’ve had some good rain and the heat hasn’t come on big time,” said Dvorak. “When you get up into the 90s, plants stop producing roots and get into survival mode. I’m hoping the hot weather holds off so these plants can become settled into their living conditions.”
Determining what kinds of plants will survive is a slow process, he said. “In a region with weather like Texas, setbacks should be expected. It’s going to take time to learn what works.”
Dvorak has also been researching green walls in other locales.
A few years ago in Chicago, one got built and in its first summer growing season it looked great,” said Dvorak. “Then winter hit, all the plants died, and people said living walls wouldn’t work in Chicago.’”
“But you can’t say that,” he said. “What you can say is that those plants didn’t work that year using that particular green wall design.”
In May, Dvorak traveled to Santiago, Chile, where a 14-story green wall was established in 2011, and found that 60 percent of the wall is dead and is being replanted.
“Does that mean it’s a bad living wall design, or that it’s not the right plant for that particular design, or is it a combination of both?” he said. “It’s a matter of finding out what works and what doesn’t.”
Public interest in green roofs and green walls is rising, said Dvorak, resulting in a growing market and new job opportunities. Kirk Laminack, a graduate student in the Department of Horticultural Sciences who graduated this spring and had been with Dvorak’s project since the beginning, was hired by a botanical garden in North Carolina to a fulltime green roof and green wall systems position.
“People are really interested,” said Dvorak. “The question is how do you do it?”
The three-year, $300,000 project is led by Dvorak, Don Conlee, associate professor of atmospheric sciences, and Astrid Volder, who began the project on the Texas A&M horticulture faculty but now teaches at the University of California, Davis.
It’s funded by a Texas A&M Tier One Program grant aimed at enhancing students' preparation for the workplace and society through high-impact, interdisciplinary learning experiences.