Tennessee Turfgrass – Tom Samples and John Sorochan, University of Tennessee, Department of Plant Sciences
Bermudagrass, an aggressive sod-forming and warm-season turfgrass, most likely originated in Africa and south and southeastern Asia. It is believed that the species was introduced into the U. S. in the mid- 1700’s from seed in hay used as bedding on ships sailing from Africa to America. Some turf-type bermudagrasses in today’s marketplace are non-seed bearing hybrids of two Cynodon species, C. dactylon (Common) and C. transvaalensis (African), and must be vegetatively established. Others are improved varieties of ‘Common’ bermudagrass and are prolific seed producers often referred to as ‘seeded-types’. Plants spread by both above- and below-ground stems referred to as stolons and rhizomes, respectively.
Bermudagrass grows best in open areas receiving full sun and although a limited number of varieties have improved shade tolerance, the species is generally not well adapted in moderately to heavily shaded areas. Leaves and stems become straw-brown as plants enter dormancy each fall. A healthy, actively growing bermudagrass turf is dense, uniform, resistant to weed invasion and capable of quickly recovering from wear injury. Under ideal growing conditions, and in nutrient-rich soils, newly planted sprigs of several varieties may grow at the rate of ¾-inch or more per day.
The species tolerates sandy to clayey soils, however both hybrid and common bermudagrasses grow poorly in infertile soils that remain wet for an extended period. Depending on management intensity level, the nitrogen (N) fertility requirement of bermudagrass usually ranges from ½ to 1½ lbs. of N per 1,000 sq. ft. per growing month. Bermudagrass turfs are often routinely dethatched and are susceptible to several patch diseases including pink snow mold (Microdochium nivale), large patch (Rhizoctonia solani) and spring dead spot (Ophiosphaerella spp.). Common insect pests include armyworm (Pseudaletia unipuncta), fall armyworm (Spodoptera frugiperda) and white grubs (larvae of several species of Scarab. beetles). Winter annual weeds such as annual bluegrass (Poa annua), common chickweed (Stellaria media), henbit (Lamium amplexicaule) and purple deadnettle (Lamium pupureum) may appear in bermudagrass turfs during winter dormancy. Several perennial weeds with energy-rich, below-ground bulbs or tubers such as yellow nutsedge (Cyperus esculentus), green (Kyllinga brevifolia) and false-green (Kyllinga gracillima) kyllinga, wild garlic (Allium vineale) and wild violet (Viola spp.) can become problematic as they compete with bermudagrass plants for water, nutrients, light and space.
Identification. Both the upper and underside of leaves of bermudagrass may be smooth or hairy. The midvein appears as a slight fold in the center of the leaf and runs parallel to the edges. The leaf tip is sharply pointed and the ligule is a fringe of hairs. The collar is continuous and hairs are visible on the collar region at the junction of the leaf blade and sheath. Plants have no auricles (small outgrowths from the base of the leaf blade at the collar). The seedhead has from three to six or more spikes atop a flowering stem and resembles a bird’s foot.
Vegetative/Clonal Types. The first recorded release of an improved, turf-type bermudagrass variety occurred in 1947 with the release of ‘U-3’ by the United States Golf Association (USGA) in cooperation with the United States Department of Agriculture (USDA). This variety was found growing in Savannah, GA in 1938. In 1956, the soft, low-growing sterile hybrid variety ‘Tifgreen’ was jointly released by the Georgia Agriculture Experiment Station (AES) and the USDA- Agricultural Research Service Crops Research Division (ARS/CRD). ‘Tifway’, another sterile hybrid variety selected and cooperatively tested by the USDA, the Georgia Coastal Plain Experiment Station (ES), and the U. S. and Southern Golf Associations was released for production to sod growers in 1960. The USDA and the University of Georgia Coastal Plain Experiment Station jointly released ‘Tifdwarf’, a dwarf mutant of Tifgreen, in 1965. It has a darker green color and shorter leaves, stems and internodes than Tifgreen. Tifdwarf also establishes slower than Tifgreen when sprigged at the same planting rate. For many years, these three varieties with the prefix ‘Tif’, two recommended for use on golf greens and intensely managed lawns, the other for golf course fairways, sports fields and lawns, have served as standards to which new bermudagrasses are compared.
Vegetatively established varieties marketed throughout Tennessee vary in overall quality, and in traits including leaf texture, color, stand density, vertical and lateral growth rate, water use rate, low-temperature hardiness, and disease and insect resistance (Tables 1 and 2).
Vegetative, Ultra-dwarf Clonal Types. Ultra-dwarf varieties such as ‘Champion,’ ‘Mini-Verde’ and ‘TifEagle’ have replaced both Tifgreen and Tifdwarf as varieties of choice for newly constructed or renovated greens in Tennessee (Table 3). They generally have shorter internodes, higher shoot densities, better overall turf quality and the ability to withstand lower cutting heights. Along with the improved overall putting surface of the ultra-dwarf bermudagrasses comes the need for a change in ‘conventional’ bermudagrass greens management practices. Research demonstrates that the ultra-dwarf bermudagrasses may be shallowly rooted and quickly produce excess thatch. Due to their very high aerial shoot densities, they may also prove challenging to topdress with sand meeting USGA specifications for putting green construction. Routine vertical mowing and applications of an appropriate wetting agent and plant growth regulator may be required. At times, two layers of winter protective blankets may be necessary to prevent severe low-temperature injury and desiccation in winter.
Seeded Types. Historically, much of the bermudagrass seed marketed in Tennessee is harvested and processed in Arizona and New Mexico where two harvests may be possible annually. Common, also referred to as ‘Arizona Common’ bermudagrass, continues to be planted to establish lawns, sports fields, utility turfs and erosion-resistant groundcovers throughout the south. However, Common bermudagrass is generally lighter in color, less dense, coarse textured, has a limited root mass and is more prone to low temperature and frost injury than many improved common types and vegetatively established hybrids. As a result, seed sales of the newer, improved turf-type common bermudagrasses continues to rise.
The varieties ‘Yukon’ and ‘Riviera’ released by Oklahoma State University in 2000 and 2001, respectively, have better quality, low-temperature tolerance, rooting and spring dead spot resistance than ‘Arizona Common’. Other improved common bermudagrasses marketed in Tennessee at this time include ‘Gold Glove’, ‘Mirage 2,’ ‘Monaco’, ‘North Shore SLT’, ‘NuMex-Sahara’, ‘Pyramid 2’ and ‘Royal Bengal’. Two or more varieties may be blended and sold in an effort to take advantage of the improved traits of each and provide buyers varieties that will establish and persist in several different microenvironments.
Turfgrass breeders continue to develop and evaluate new bermudagrasses. The National Turfgrass Evaluation Program (NTEP) “is designed to develop and coordinate uniform evaluation trials of turfgrass varieties and promising selections in the United States and Canada. Test results can be used by national companies and plant breeders to determine the broad picture of the adaptation of a cultivar. Results can also be used to determine if a cultivar is well adapted to a local area or level of turf maintenance”.
In addition to the sterile, vegetatively established bermudagrasses, green industry professionals may recognize many of the seeded types entered in the six NTEP National Bermudagrass Tests. Twenty-one vegetatively established and seven seeded varieties including ‘NuMex-Sahara’ and ‘Sonesta’ were entered in the first National Bermudagrass Test (NBT) in 1986. There were 10 vegetatively established and 16 seeded entries including ‘Cheyenne’, ‘Jackpot’, ‘Mirage’, ‘Primavera’ and ‘Sundevil’ in the 1992 NBT. Of the entries in the 1997 NBT, 18 were seeded types including ‘Blackjack’, ‘Blue-Muda’, ‘Majestic’, ‘Princess’, ‘Pyramid’, ‘Riviera’, ‘Savannah’, ‘Shangri La’, ‘Southern Star’, ‘Sundevil II’, ‘Sydney’ and ‘Transcontinental’, and 10 were vegetatively established. Twenty-nine of the 42 entries in the 2002 NBT were seeded types including ‘Contessa’, ‘LaPaloma’, ‘Mohawk’, ‘Panama’, ‘Southern Star’, ‘Sovereign’, ‘Sunbird’ and ‘Yukon’. Twenty-six of the 31 entries in the 2007 NBT were seeded types including ‘Gold Glove’, ‘Hollywood’, ‘Princess 77’, ‘Pyramid 2’, ‘Royal Bengal’, ‘Sunsport’ and ‘Veracruz’. The most recent NBT planted in 2013 contained 13 vegetatively established and 29 seeded types including ‘Monaco’ and ‘North Shore SLT’. A number of entries designated by letter and or number in this test will most likely be marketed as named varieties in the future. For more information regarding the disease and insect resistance, cold tolerance and overall performance of individual bermudagrass varieties, please visit the NTEP Website, http://www.ntep.org.
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Turfgrass and Environmental Research Online (http://usgatero.msu.edu/v08/n16.pdf). USGA. Volume 8, Number 16, AugustREAD THE ISSUE