Going Native the Texas Way
George W. Bush Presidential Center brings the prairie to the SMU campus
Ground breaking for the George W. Bush Presidential Center took place Nov. 16, 2010. The facility was dedicated and opened on April 25, 2013.
Photos courtesy of Manhattan Construction.
Visitors to the George W. Bush Presidential Center see a native Texas prairie consisting of drought-resistant grasses and beautiful native wildflowers. The foundation for this ecosystem begins far below the grasses and Texas-tough ornamentals that frame the Presidential Center. Recreating that prairie required extensive cooperation among a number of firms as they worked toward the goal of fulfilling the vision of President Bush and Mrs. Laura Bush's love for that landscape.
"Our initial observation as we drove around in Dallas was the high number of massive lawns with water-intensive green grass," says Herb Sweeney, senior associate, Michael Van Valkenburgh Associates, Inc., (MVVA). Based in Cambridge, Mass., MVVA was selected as the landscape architectural firm for the Presidential Center completed this year with Sweeney as project manager. MVVA has received numerous awards for its projects including Pennsylvania Avenue at the White House, and The City+The Arch+The River competition at St. Louis.
Along with MVVA, the design team included soil scientist expertise from Olsson Associates, Lincoln Neb., irrigation specialists Jeffrey L. Bruce and Company, Kansas City, Mo., and the Lady Bird Johnson Wildflower Center at the University of Texas at Austin. The design team designed the soil profiles and selected the soil types used on the project, the foundation for the water management and native prairie.
The extensive lawns with green grass in the Dallas area contrasted sharply with the perception of Texas in a water crisis. "Water is the most critical environmental concern in Texas, if not the entire country," Sweeney says. From an ecological perspective, the Presidential Center landscape design exhibits major environmental approaches to landscape management through the components of soil management, and native plant and turf selections. These native selections were based primarily on research by the Lady Bird Johnson Wildflower Center, University of Texas, Austin.
Campus and community
The Presidential Center is located on the campus of Southern Methodist University (SMU), Dallas, a 23-acre site with a 15-acre park. Through careful use of soils, water, topography, sun and plant species, a native Texas landscape was recreated that not only frames the site, but also helped in earning the Platinum-LEED certification. Extensive attention to the development of the soil composition and water management, complemented by research-based, native plant selection, provide a site that reduces irrigation needs and allows complete organic landscape management.
The design of the Presidential Center anchors it not only to the SMU campus but also to the community.
"People feel a sense of arrival on campus," says Sweeney, citing the Presidential Center's native landscape located on the east side of SMU campus. By recreating a native landscape, once so common in the region but now overwhelmed, the Presidential Center not only documents the George W. Bush presidency but also contributes to the community. Its many paths and partially shaded areas of turfgrass frame the campus, inviting visitors as well as community residents to enjoy the changing seasons of a native landscape.
Starting with the base
The site's design, soil composition and plant selection facilitate water management. The soil composition is the key element in the success of the water management program and the ability of native plants to thrive. The soil profile retains the water or filters it through the landscape making its way to an on-site cistern where it is stored. Soil compaction at the site has occurred over the many years of development culminating with the construction of the 226,565-square-foot building.
Texan and former First Lady Lady Bird Johnson (1912-2007) popularized wildflowers across the nation. Many native Texas wildflowers beautify the Center.
Photo courtesy of Southern Botanical.
About 100,000 cubic yards of existing soils from building excavation and other construction activities were retained on site to create the landforms that direct stormwater.
A second mission in the soil profile development was to recreate an environment with rich organic material on top that would allow native plant roots to go deep imperative. Workmen imported about 650,000 cubic yards of soil from Streetman, Texas, to improve the site's soil. They then augmented the planting area with a 12-inch layer of mature compost layer generated from woody materials, grasses and lawn cuttings. As far as possible, the resulting soil replicates the Texas blackland prairie topsoil that had developed over centuries. The depth of manufactured planting soils varies based on plant types.
Manhattan Construction, headquartered in Tulsa, Okla., was the general contractor responsible for implementation of the design. "We served as the landscaping liaison between MVVA and subcontractors," reports Travis Mmaiwelmal, the firm's project engineer in its Dallas office.
HABITURF Incorporates Three Native Blends
The Lady Bird Johnson Wildflower Center at University of Texas at Austin developed HABITURF, the mixture of turf species selected for use for the George W. Bush Presidential Center site on the SMU campus. Mark Simmons, director of research and design consulting, led the research and development of this native blend.
Praire grasses such as Big and Little Bluestem and Indian grass evoke the Texas landscape of yore.
Photo courtesy of Lady Bird Johnson Wildflower Center.
HABITURF offers a natural, native look that requires considerably fewer inputs, thereby reducing costs and damage to the ecology. HABITURF establishes quickly, survives well with minimal watering and requires less mowing and weeding to retain an attractive, natural appearance. The grass is a mix of buffalograss, blue grama and curly-mesquite. HABITURF is well adapted to the Texas climate and other hot, dry regions of the U.S. Southwest.
The researchers' initial thinking was based to some degree on native grasslands in natural conditions. "Natural grasslands offer a case in point. Under natural conditions, few grasses occur as monocultures. Most occur in assemblages with other grasses and forbs," says Mark Simmons, director of research, Lady Bird Johnson Wildflower Center Extensive. Research with experimental plots first established in 2007 in Austin, Texas, produced encouraging results that led to the commercial development of HABITURF.
While the three species are different, the grasses exhibit almost identically shaped leaves and color and produce even-textured, dense turf that does well in full sun but tolerates 50 percent shade. After establishment when irrigation is required daily for the first 10 to 15 days, depending on conditions, two watering per week for the next month, followed by two wettings per month is sufficient during the growing season of March through November.
Irrigation may be discontinued if necessary after the turf is established for about three to four months with the turf allowed to go "drought dormant." The native grasses will go brown but will green up when rains return. During droughts of more than six weeks, the turf can be irrigated every five to six weeks to keep the grass alive.
HABITURF is mowed to three to four inches, giving it improved weed resistance and tolerance to light to moderate foot traffic. For heavier traffic, a height of 6 inches may be maintained with at least a 4-inch height recommended for overwintering. Returning grass cutting to the soil generally eliminates annual feeding. If feeding is desired on high-use sites, living compost or compost tea with aeration is recommended.
Catching the rainwater
Stormwater that falls on the site, including building roofs and parking lots, is conducted through vegetated bioswales to a wet prairie that serves as a natural filter and removes sediments. Water is fed into an underground tank that stores the water for reuse as irrigation water as needed primarily during an establishment period for the native Texas prairie plants.
The stormwater management contrasts with the trend in residential building of getting stormwater off properties into a storm sewer system as quickly as possible. The Presidential Center site captures the water, retaining it for growing plants or directing it to the 250,000-gallon underground storage system where it is reused as irrigation water as needed. This exceptionally large cistern was a significant undertaking for the project and expresses the level of commitment on the part of the Presidential Center to water conservation.
Two major stonework features help filter water and control movement of silt that may flow down bioswales. These bioswales filter contaminants through a specialized selection of grasses, sedges and planting soils. Large stone boulders slow the flow of water and help prevent erosion.
The site has less than half the stormwater inlets that would normally be found on a site this size. Instead, the water drains through the soil, which filters it, holding water for plants, and excess water drains to the storage system. A sub-soil drainage system of storm lines drain of corrugated black drainage pipe covered with drainage gravel drains water to the storage cistern. A Rain Bird irrigation system with 200 zones was installed and is mostly a temporary system that will be turned off after one to two years after plant establishment.
The Manhattan Construction Company built the $250-million Center.
Photo courtesy of MVVA.
Recreating a legacy landscape
Mark Simmons, director of research, Lady Bird Johnson Wild- flower Center, based at the University of Texas in Austin, worked closely on the project. The Wildflower Center has conducted extensive research in fulfilling its mission to increase the sustainable use and conservation of native wildflowers, plants and landscapes. While bluebonnets are well known for the spectacular early spring displays, the Presidential Center shows these Texas jewels off in a wildflower meadow that becomes an integral part of the city for all residents and visitors to enjoy. A shortgrass prairie features Big and Little Bluestem, Indian Grass and switchgrass among other grass species. These grasses cover gentle and steep slopes and are interspersed with wildflowers that include horsemint, coneflowers, daisies and Indian Blanket.
A major advantage of this shortgrass prairie is that once the plants are established, no irrigation will be required thereby contributing extensively to reducing water input requirements of the site.
Native grass seeds are carefully weighed and mixed in small batches.
Photo courtesy of Southern Botanical.
The turfgrass blend HABITURF, developed and tested at the Wildflower Center, is featured at the formal entrance to the Presidential Center as well as on all other lawns and turf paths throughout the site. Seeding was done by hand, and weighing the mixture, which consists of three species, was required to assure the appropriate mix.
Simmons says, "The native short grass species are well adapted to climate and soil conditions in areas with infrequent and erratic rainfall." The importance of grass species that requires little maintenance and low water input is crucial to the overall sustainability of the site.
Jason Craven, president, Southern Botanical, Inc., worked with Metheny Landscape of Dallas on soil installation. Southern Botanical installed plants and grass seed, and continues to maintain the site incorporating the required strict organic maintenance process.
Craven notes that the organic compost was tested for its maturity as well as active biology by the food soils web. "Liquid biological amendments were introduced to encourage the soil biology and beneficial fungi. Special care was taken to make sure that all material used was free from weed seeds," Craven says. Invasive species are pulled by hand, and in this case, invasive species refers to any plant not specifically designated and planted at the site.
Limestone seatwalls provide visitors with quiet places to sit, rest and contemplate the legacy of the George W. Bush presidency (2001-2009). And enjoy the beauty of native Texas plants, too.
Photo by Elizabeth Felicella for MVVA .
Lawns are mowed at infrequent and varying intervals to not only reduce environmental impacts but also encourage the desired species to thrive and choke out any undesired material. "Soil is tested before any organic fertilizers are applied, and applications are tailored specifically to the soil needs," Craven noted.
These organic maintenance processes greatly reduce inputs to the site. With reduced inputs, costs and environmental impacts are both greatly reduced. The organic maintenance, limited irrigation and reduced inputs of all types are facilitated by the development of soil and water management that supports establishment of the native prairie, and will allow this prairie to thrive.
Nancy Riggs is a freelance writer from Mt. Zion, Ill., and has been covering the green industry for Turf for more than 20 years. Contact her at NFRIGGS@aol.com.