Grass the needs less mowing and water is a project for scientists across the country.
Clipped-grass turf is the most heavily used material in most American landscapes. The NASA researcher Cristina Milesi used satellite imagery to estimate that lawn occupies some 49,000 square miles of the United States, and it’s increasing by roughly 600 square miles per year, according to a study conducted by Paul Robbins and Trevor Birkenholtz of Ohio State University’s Department of Geography.
Yet, since the 1950s, landscape architects have typically ceded decisions concerning this vast area to turf-industry technicians. Turf became an industrial product after World War II. Which grass to use was dictated by mowers, sprayers, blowers, and spreaders, and choices were limited to a very few varieties of grasses, such as Kentucky bluegrass (Poa pratensis) and hybrid Bermuda grasses (Cynodon spp.), that lent themselves to chemical maintenance. Today, though, new alternatives are emerging that landscape architects can use to create healthier and more aesthetically dynamic models for what a domestic grassland can be—a source of environmental renewal rather than an ecological villain. It will also please the increasing numbers of clients who dislike not only the sterile monotony of conventional turf and its high maintenance costs, but also, more critical, the threat that the required maintenance chemicals pose to kids, animals, and communities.
Any well-designed planting begins with careful analysis of the site, soil, regional climate, and adapted plants. Turf is no exception—which is why the emergence of new and unconventional grasses is such an important development. Many of these new grasses are still not available at the retail level locally, and few are available as sod. This situation, however, could begin to change if landscape architects exert their influence and create demand for them.
The place to start looking for alternative turfgrasses is at the experiment stations of major land-grant agricultural universities. These institutions have accumulated copious data about the ways various grasses perform in challenging circumstances, providing an invaluable guide to the landscape designer in pursuit of sustainability. They’ve bred many new, hardier cultivars of traditional turf species and have domesticated species that traditionally weren’t regarded as suitable for lawns. Here are some things to consider about the more promising varieties and mixes, by region:
Because of their region’s need to conserve water, researchers in the semiarid West became pioneers in exploring alternatives to the traditional lawn. Work began more than 20 years ago to domesticate and refine better adapted, native grass species such as blue grama (Bouteloua gracilis), western wheatgrass (Pascopyrum smithii), and, most famous, buffalo grass (Bouteloua dactyloides). In some respects, buffalo grass has become too popular, landscape designers’ default “environmentally friendly” lawn alternative even in regions such as the Northeast, where this species is poorly adapted and can be maintained only with special care.
The three species mentioned above all can provide attractive, low-input turfs on their native ranges. A more diverse and more versatile new addition to this group is “Habiturf,” a trademarked lawn-seed mix introduced in 2013 by the Lady Bird Johnson Wildflower Center at the University of Texas at Austin. This mix includes three species of native grasses—blue grama, buffalo, and curly mesquite (Hilaria belangeri), all of which are raised commercially for seed—plus as many as four other short-grass prairie species that are included when their wild-collected seed is available. The result is a soft, green, relatively weed-resistant turf that requires no fertilization and little irrigation. Mark Simmons, Affiliate ASLA, the director of research and consulting at the Wildflower Center, led the effort to create this mix. Simmons notes that half an inch of water applied every three weeks during hot, dry weather will keep Habiturf green through the summer, although the frequency of watering can be cut back to once every five to six weeks if summer dormancy and a temporarily brown lawn are acceptable. Habiturf may be left uncut if eight-inch turf is tolerable, or it can be mowed to a height of three to four inches.
It’s important to note that all of the western alternatives described above are warm-season bunchgrasses. That is, they do not spread by stolons like Kentucky bluegrass and so take longer to mature into a more or less uniform ground cover, and they turn tan colored with the onset of cold weather in the fall, not regreening until mid- to late spring. Progressive designers, however, are learning to relish the regional flavor of these grasses and the soft prairie texture that they lend to a landscape.
Marc Pastorek, a prairie restorationist in New Orleans who consults throughout Louisiana, Mississippi, and Alabama, recommends pineywoods dropseed (Sporobolus junceus) as the ideal native grass for a lawn in the southern coastal plain. This warm-season bunchgrass, native from the Gulf Coast of Texas through the Carolinas, naturally forms dense tufts of needlelike but soft-textured foliage that responds to mowing by forming a soft, low-maintenance turf.
Pastorek is also testing, with the collaboration of three research stations in Louisiana and Texas, a grass mix that could provide an analog to buffalo grass for warm and humid regions. This turf is a blend of pineywoods dropseed with slender little bluestem (Schizachyrium tenerum), arrowfeather threeawn (Aristida purpurascens), splitbeard bluestem (Andropogon ternarius), and Elliott’s bluestem (Andropogon gyrans) and grows to a height of 12 inches; it requires just one mowing a year, in February.
Although the northeastern states remain a stronghold of traditional turf, researchers at Rutgers, the State University of New Jersey, have been testing and promoting better adapted, more sustainable turfs for the region. Researchers at the university’s Center for Turfgrass Science have worked with the National Turfgrass Evaluation Program to identify cultivars of less commonly used species, such as the fine fescues, which are notable for their attractiveness, disease resistance, and low maintenance needs, and which form the basis of the “no-mow” lawn-seed mixes marketed by a number of companies. (In fact, fine fescues typically require at least one or two mowings a year—and as many as four or five if a neater look is desired—but they are useful for places such as historic cemeteries, where mowing is a major expense as well as the principal source of damage to headstones and monuments.) It’s best to avoid the off-the-shelf mixes and instead assemble a custom mix of cultivars adapted to the needs of the client; and, of course, the mix should be resistant to locally prevalent turf diseases.
Another unconventional species that Rutgers horticulturists are promoting is rough bluegrass (Poa trivialis), a cool-season grass that has a fine texture and remains green through the winter. This species has been treated as a weed by the turf industry because it is lighter in hue than Kentucky bluegrass and less upright in its growth. Its success as a “weed,” however, reflects its superior adaptation to moist, semishaded sites where other cool-season turfgrasses don’t flourish. Improved cultivars such as Darkhorse and Racehorse offer richer, more attractive colors.
Yet another overlooked species is sheep fescue (Festuca ovina). Traditionally reserved for erosion-control plantings along highways, sheep fescue is a useful and attractive, low-input turf for challenging sites in the Northeast. It’s a cool-season bunchgrass that is nearly invulnerable to drought and tolerates poor, acidic soils. Like all the bunchgrasses, this species takes time to knit together into a uniform turf, but once established it requires almost no irrigation and no fertilization, especially when combined with white clover. It makes a soft-looking, fine-textured lawn that requires mowing only a couple of times a year. Azay Blue is a cultivar with an attractive blue-green hue.
AN OPPORTUNITY FOR BIODIVERSITY
The greatest environmental liability of the conventional American lawn, after its dependence on chemicals and constant irrigation, is its lack of biodiversity. The main creatures it provides habitat for are mowers. There is, however, a movement beginning to identify perennial grassland flowers whose low stature and fine foliage make them compatible aesthetically and culturally with turf. Most of this activity has been taking place in the Northeast, although Simmons has begun trials of this sort in Texas.
In Mystic, Connecticut, Charles Boos, the owner of Mystic Natives Consulting Services, has been planting test plots of native grasses and wildflowers adapted to various conditions. He has, for instance, interplanted purple love grass (Eragrostis spectabilis) with dwarf cinquefoil (Potentilla canadensis) in an exposed spot where the soil has been infiltrated with road salt and sand. He has also interplanted tufted hairgrass (Deschampsia cespitosa) and common goldstar (Hypoxis hirsuta) in a shaded spot. Results have been mixed. Blue-eyed grasses (Sisyrinchium spp.), grassy-leaved relatives of irises, “play nice,” as Boos puts it, coexisting well with other wildflowers and grasses, whereas wild strawberry (Fragaria virginiana) tends to crowd out other plants around it.
Bunchgrasses are key to the success of these interplantings, because their less tightly knit carpets are more penetrable to wildflowers. And the biodiverse turf thus created provides habitat for pollinators such as bees and butterflies, whose numbers have been declining, as well as other insects, helping to return a designed landscape to the status of a functioning ecosystem. It can also make the lawn a refuge for grassland wildflowers in areas such as the Northeast, where formerly open fields are being overtaken by second-growth forest.
My own experiment interplanted naturalized bulbs of native violet wood sorrel (Oxalis violacea) in a sheep-fescue turf in western Massachusetts. Once relatively common in southern New England, violet wood sorrel currently persists in Massachusetts in just five wild colonies, and only about 20 in New England as a whole, according to a 2002 conservation plan created by Thomas Mione, a professor of biology at Central Connecticut State University, for the New England Wild Flower Society. Including it in turf in this way may make the difference between keeping a viable population of violet wood sorrel and its disappearance from the region.Thomas Christopher is a horticulturist who specializes in sustainable lawn design and is the owner of Smart Lawn LLC.