Pardon our Green Roof Dust
Habiturf, Other Greenery Tops Café Soon
A steel-framed pergola (or arbor) is visible from above the southern wall of the Wildflower Center Café windows. The pergola is part of Robb's Roost, which is being updated as a walk-through green roof demonstration and research space. Photo by: Bruce Leander.
Thanks to a $44,637 grant from The University of Texas at Austin's Green Fee Committee, the Wildflower Center is updating the patio above the café as a vegetated roof demonstration space.
Lynda Johnson Robb, eldest daughter of Lady Bird Johnson and Lyndon Baines Johnson, provided funds in the early 1990s to develop the space known as Robb’s Roost. The flooring of this space halfway up the stairs of the San Antonio Tower will be retained and updated with a 4-foot wide metal grate for walking. The walkway will be suspended above a groundcover grown in a green roof planting mix developed by the Center. The metal walkway will serve as the flooring that allows visitors access to two planting beds and an updated patio area for resting and enjoying the views.
“People know about green roofs, but this will be a chance for them to get up close and know what that really means while actually walking through a green roof space and hanging out there,” says John Hart Asher, the Center environmental designer who worked with the Horticulture Department on the space.
One narrow bed will run along the entire east edge of the roost, and will display a mixture of native succulents and cacti that the Center’s Ecosystem Design Group selected. These plants were picked for their potential to thrive based on previous residential green roof projects they’ve consulted on, as well as findings from the Center’s on-site research about what natives work best on green roofs in hot Southwestern climates.
False aloe, coral yucca and Texas bluebonnets will be among the native plants in the narrow bed. The other plot at the northwest corner of the patio will feature the Center’s Habiturf® native lawn mix ringed with the same Texas natives, including spineless prickly pears and candelilla. A trellis of coral honeysuckle will extend along that bed’s western edge and provide nectar for hummingbirds.
The redesign is meant to demonstrate the beauty of native plants as a part of vegetated roofs and teach about the benefits of green roofs the Wildflower Center is studying, such as keeping buildings cooler and helping purify and slow the movement of storm water. By this summer, visitors will see a groundcover of snake herb poking through the walkway’s 1-inch spaced bars. The patio across from the entrance of the green roof garden will be redesigned to enhance seating under a pergola for viewing the green roof beds and taking in overviews of the central gardens below.
The pergola’s steel columns will be topped with new lattice-work, likely of wood. UT’s chapter of the American institute of Architect Students is redesigning the pergola and will install the new lattice-work before Robb’s Roost re-opens in May. “We are redesigning the space thanks to the Green Fee Committee grant that is funded by UT student fees, and we’re really grateful for that and the students’ participation,” says Andrea DeLong-Amaya, the Center’s horticulture director.
Besides showing visitors how native vegetation can enhance a small space, this demonstration should attract native birds and other wildlife. It will also allow guests to learn about a new green roof planting media the Center has developed. Many green roofs use a planting mix that contains elements like sand that are mined, or components like coconut coir fibers that are easily replenished, but are shipped from overseas. Transporting those materials adds to a green roof’s carbon footprint.
To make the most “green” vegetated roof possible, the Wildflower Center has developed a planting media whose components are all Texas-derived, recycled elements. The succulents and cacti in the Robb’s Roost garden will be growing in 4 inches of this mix once installed in early March.
Among the drought-tolerant native plants whose minimal water needs will be tested in the Robb's Roost green roof study will be: spineless prickly pear, coral yucca and Texas bluebonnets. Photos by Joseph Marcus and Bruce Leander.
“We want to be holistic about all the sustainable steps we’re taking with green roofs — not just using native plants that tend to require less resources,” Asher notes.
Equally important, the bed with Habiturf will be studied to see how little irrigation it requires as part of a 2014 study being funded by the UT green fee fund. The mixed catci and succulent bed will also be part of this study, and will not likely receive any irrigation.
Since water conservation is becoming a priority in so many states, we want to look at minimizing or eliminating irrigation of green roofs when that is best,” Asher says, “and this study will allow us to really dial in on what an appropriate water regimen is.”
The Café green roof redesign was made possible by pro bono work from Overland Partners (architectural drafting) The Garland Company (green roof technology and build consultant), QA Construction Services (installation), civil engineering consultant Patrick Sullivan and other donors.