Tennessee Turfgrass – Jay McCurdy, Ph.D., Associate Professor, Mississippi State University
Golf course designers and maintainers are increasingly interested in low-maintenance rough and natural areas. Labor shortages and maintenance costs are partially responsible for this trend. The general public’s growing interest in the environmental benefits of golf courses also contributes to the trend. Numerous sources establish the benefits of native and natural roughs. Although not discussed in length, benefits include:
• Reduced inputs, such as fertilizers, pesticides, fuel, equipment hours, and labor costs
• Improved stormwater retention and runoff water quality
• Temperature modification
• Wildlife habitat inclusion
This article covers several important topics regarding native golf course roughs in the southeastern United States, including species selection, establishment, and maintenance.
Southeastern states share similar environmental and socioeconomic conditions that influence course design and play. These conditions, while not unique, distinguish southeastern golf course design and maintenance from that of other regions. For instance, many architects and aficionados desire the aesthetics of a links-style, fine fescue rough, but in the Southeast, this is rarely practical or sustainable.
The Southeast’s humid subtropical climate is characterized by warm and moist summer months. Annual rainfall can exceed 50 inches. Much of that rainfall occurs during the active growth period of warm-season plant species, which dominate the playing surfaces where golf is played year-round. Contrast this with the temperate oceanic climate of Scotland, for instance, where annual rainfall is roughly half that of the southeastern United States and the temperature range is ideal for cool-season species. For these reasons, species selection, culture of native areas, and expectations for golf courses in the southeastern United States should be soundly based.
It is important to differentiate native and naturalized species. Native plants originated locally and predate European settlement. Naturalized plants are not native but grow, reproduce, and maintain viable populations without human intervention. These definitions may seem academic, but an owner’s or architect’s specification of one or the other may have real and lasting consequences.
Natural areas in the southeast are not limited to grasses. They may be composed of trees, broadleaf forbs, sedges, and rushes. Each of these species plays an integral part in a healthy ecosystem.
Many American golfers and superintendents are familiar with the look of fine fescue roughs on links-style courses, such as Chambers Bay or Oakmont. Unfortunately, fescues often fail to persist in the mid to coastal Southeast and are rarely “low maintenance.” Despite the availability of many suitable native and naturalized grasses, superintendents are often unfamiliar with their characteristics.
Tall fescue (Festuca arundinacea) is common in golf course natural areas throughout the Southeast. It is a cool-season grass native to Europe and Asia but has been naturalized in many places outside of its native range. Many pastoral golf settings (Sweetens Cove, Old Waverly, and Jackson Country Club) have mixtures of tall fescue and the native warm-season grasses little bluestem and broomsedge. Tall fescue is only moderately drought tolerant compared to most warm-season alternatives; nevertheless, it persists well in much of the mid and deep South. As a cool-season perennial, it is best established in the fall. It tolerates relatively low mowing heights in the moderate climate of the Southeast’s transition zone but generally does not require mowing to propagate by seed, as seed heads ripen in midsummer. The further south one goes, the less tolerant of mowing it becomes. For this reason, it grows well in complex with other species but is difficult to maintain as a monoculture. Frequent reseeding is required if monoculture stands are desired.
Native Warm-Season Species
Warm-season species predominate power line and transportation rights-of-way throughout the Southeast, and the golf course industry has renewed interest in including them in native roughs. This trend seems to have gained traction after Pinehurst No. 2 renovated mown rough in favor of wider fairways surrounded by penal vegetation and natural waste areas in 2011. There has since been a growing demand for that same aesthetic, unfortunately often without proper consideration of costs, plant availability, or agronomic practicality. What works in sandy Coastal Plains soils rarely works in the chalky prairie soils of the Black Belt or the red dirt of the Piedmont. Some species that work well across almost all southeastern environments are described below.
Little bluestem (Schizachyrium scoparium) is perhaps the most prevalent native warm-season species on golf course roughs in the Southeast. It tolerates most soil pH conditions and is relatively easy to establish from seed. Commercially available varieties and local populations may have different heights, plant vigor, and even color. When growing in rich soils as a monoculture, little bluestem can reach heights greater than 5 feet. Under typical conditions where it is paired with tall fescue or bermudagrass, however, its height may be less than 3 feet.
Bushy bluestem (Andropogon glomeratus) has a large fluffy inflorescence. It is common in open fields and waste areas of the southeast. It grows well alongside its equally as common cousin broomsedge (Andropogon virginicus). Both prefer acidic soils but grow well in almost all low-maintenance areas. These two species are challenging to propagate by seed because of a fluffy appendage that makes them difficult to spread or drill. If using a drill, it should be equipped to handle fluffy seed types.
Other Native Species
In addition to those previously mentioned, several warm-season grasses tolerate full sun, including purple muhly grass (Muhlenbergia capillaris), purple top tridens (Tridens flavus), wiregrass (Aristada species), and prairie dropseed (Sporobolus heterolepis). Height and biomass can be an issue with lowland and upland switchgrass (Panicum virginicum), big bluestem (Andropogon gerardii), and indiangrass (Sorghastrum nutans), but they too can be attractive additions.
Very few native warm-season grass species thrive in shaded conditions, such as woodland margins. Indiangrass (Sorghastrum nutans) or upland switchgrass can persist, but these plants reach heights of 6 to 8 feet.
Several native cool-season grasses can be used for maintaining green color and texture through winter. They include those that are less dense than tall fescue but mimic its height and texture. These may be planted in conjunction with other warm-season grasses or may be planted alone. Southeastern wildrye (Elymus glabriflorus) needs full sun. Virginia wildrye (Elymus virginicus) does well in partial shade. Canada wildrye (Elymus canadensis) prefers moist soil and partial shade. Riverbank wildrye (Elymus riparius) does well along creeks and rivers. Bottlebrush grass (Elymus hystrics), a woodland edge species, does well under deciduous trees.
In wetland margins, lowland switchgrass may be used, but this species may reach heights of 10 feet or more. Several spartina species, including prairie cordgrass (Spartina pectinate), are common along the Gulf Coast of the Southeast. Hardy sugarcane (AKA Silver plume grass; either Saccharum alopecuroides or S. giganteum) is very tolerant of wet areas but plant height may be 8 to 10 feet.
Keys to Establishment
Vegetation control prior to tillage and planting is critical. Multiple applications of nonselective herbicides (typically glyphosate), sometimes a full year in advance, are necessary to control weeds like bermudagrass, johnsongrass, dallisgrass, and vasseygrass before seeded establishment.
While fall seeding is best for cool-season species like tall fescue, native warm-season grasses are typically seeded in the spring when soil conditions are warmer than 55 degrees. Native grasses are slow to establish and require some additional consideration. It may take three or more years to reach a mature, dense stand. Weed control during this time may be aided by application of Plateau (imazapic), which is safe on many native warm-season species but will control most cool-season species, including tall fescue. Plateau will control young crabgrass and will suppress bermudagrass and dallisgrass but has little effect on broadleaved weeds. The exposed soil of slowly establishing native warm-season roughs is an open invitation for warm-season annual broadleaved weeds like Virginia buttonweed, tropic croton, chamberbitter, and poorjoe. A broadleaf herbicide like Crossbow (2,4-D and triclopyr) or NativeKlean (2,4-D and aminopyralid) is often warranted during the first few years of establishment. Complicating weed control further is the fact that these native roughs can grow so tall that a standard boom sprayer cannot pass over them. For this reason, a single nozzle boomless sprayer is sometimes required for late-season applications.
Mowing and Burning
Native and naturalized species propagate by seed. Golf course superintendents may leverage this characteristic to manipulate stand density. Cool-season grasses disseminate their seeds during the summer. Warm-season grasses disseminate their seeds during the fall and winter. Seed propagation relies upon open, exposed soil, which may be achieved by grazing, mowing, or burning. Tall fescue evolved under grazing pressure rather than seasonal burning, but mowing is a common substitute. Most species native to the southeast evolved under grazing or periodic burning, and thus mowing is a viable substitute.
For playability, one may wish to decrease plant density in natural areas so that golfers can find balls. This is achieved by mowing at suboptimal times. For erosion control or aesthetics, one may wish to increase plant density. This is achieved by favoring the desired plant species. Most courses will strategically mow or burn parts, but not all, of their rough on an annual basis.
For seed dispersal and increased stand vigor of native warm-season species, mowing or burning should occur when seed heads are ripe and plant material is senesced (dry and brown). The recommended mowing height for most natives is at least 8 inches. Tall fescue tolerates relatively low mowing heights (~4 inches).
Many superintendents favor a mixed stand of tall fescue and native warm-season grasses like broomsedge and little bluestem. Shifting a population away from tall fescue and towards native warm-season grasses is easy to achieve with winter burning followed by two applications of Plateau (in roughly April and June). Alternatively, introducing cool-season species with fall seeding of tall fescue or native cool-season grasses can be aided by suppressing the growth of native warm-season species with summertime mowing.
Flowering Plants and Pollinator Habitat
Introduction of flowering plant species is rarely discussed in context with establishment of biodiverse golf course rough. The topic deserves its own essay, but the same techniques mentioned above may be used to favor the seeded establishment of pollinator-friendly forbs and wildflowers. These species are far less tolerant of the herbicides mentioned thus far. In fact, Mississippi State University research indicates that very few herbicides are safe across the typical species found in southeastern flora. The ACCase-inhibiting herbicides, like Fusilade (fluazifop), Poast or Segment (sethoxydim), and Acclaim (fenoxaprop), that control grasses, are useful during the establishment of broadleaved species and can be applied at rates that allow tall fescue and most native warm-season grasses to recover. Halosulfuron (Sedgehammer, Manage, Prosedge, etc.) is useful for sedge control and is safe across most grass and forb species. Controlling annual broadleaf weeds within mixed grass and forb areas relies upon spot treatment for control, but low rates of Image (imazaquin) or Basagran (bentazon) are moderately tolerated by established stands of many flowering plant species.
There are two approaches one might choose to establish pollinator habitat in native and natural roughs of the southeast: 1) Pollinator refuge “islands”. These islands would intentionally be forbs rather than grasses. Start clean. Prepare a seed bed by controlling all vegetation and tilling prior to seeded establishment of a seed mixture. This will result in more uniform density. Grasses can be kept at bay using repeat applications of ACCase-inhibiting herbicides. 2) Mixtures of grasses and forbs. These mixtures mimic what naturally happens in prairie environments of the southeast. Experience suggests that starting forbs in established grass is easier than trying to establish grasses and forbs simultaneously. This is because of the need for herbicidal control of many weeds during the early establishment period. A better strategy may be to establish native/naturalized grasses in years 1 and 2 then thin grasses mechanically or chemically to interseed flowering forb species in spring of a subsequent year.
Low maintenance does not mean no maintenance. These areas require a unique skillset, trained labor, specialty equipment, and knowledge. Native and natural areas are penal. Owners, architects, and other stakeholders should be involved in course design and the development of a strategy that leads to long-term success. That strategy should include flexibility and patience. This long-term approach can be aided through signage and written communication that educates golfers and helps our colleagues in the proshop. Most importantly, enjoy the process. These areas are fascinating to watch as they ebb and flow throughout the seasons.
Richard, Michael P., Jesse I. Morrison, and James D. McCurdy. “Effects of preemergence herbicides on establishment of little bluestem and sideoats grama golf course rough.” Crop, Forage & Turfgrass Management 6, no. 1 (2020): e20051.