The genus Cynodon comprises nine species with C. dactylon being the most widespread. That C. dactylon is a tetraploid with broad genetic variability serves to explain its widespread distribution. Other Cynodon species have a more limited natural distribution and are often restricted to one particular habitat. C. dactylon is highly fertile, whereas the diploid species such as C. transvaalensis rarely produce viable seed.
C. dactylon (L.) Pers is commonly called bermudagrass in many areas of the world. But, it is also known by numerous other names including "Kweekgras" (S. Africa), couch grass (Australia and Africa), devil's grass (India) and gramillia (Argentina). The variety of names given this species attests to its wide distribution and to the fact that it is the object of abuse and scorn.
In addition to being a widely used species for forage and turf, C. dactylon is a serious weed in many crops. Being a vigorous, stoloniferous grass, it rapidly invades crops in high rainfall or irrigated areas. C. dactylon is ranked among the three most troublesome weeds in sugarcane, cotton, corn and vineyards in many countries. It is a difficult weed to eradicate because of its seed production and deep rhizomes.
In the United States the distribution of bermudagrass extends from New Jersey and Maryland southward to Florida and westward to Kansas and Texas. Under irrigation its distribution extends westward to southern New Mexico, Arizona and to most major valleys in California. The development of more cold tolerant turf-type varieties of bermudagrass such as U-3 and Midiron has increased interest in the species near its northern limits. Low winter temperature is the factor that limits the northward distribution of bermudagrass.
Description. Bermudagrass (C. dactylon (L.) Pers.) is a highly variable, sod forming perennial that spreads by stolons, rhizomes and seed. Stolons of bermudagrass readily root at the nodes. Lateral buds develop at the nodes to produce erect or ascending stems that reach 5 to 40 cm (rarely over 90 cm) in height. In most Cynodon sp., leaves are borne on stems with long internodes alternating with one or more very short internodes. This characteristic gives the impression that the species has multiple-leaved nodes. Leaf sheaths are compressed to round, loose, split, smooth, sparsely hairy, up to 15 cm long, and with a tuft of hairs 2 to 5 mm long. Auricles are absent. Collar is continuous, narrow, glabrous and hairy on margins. Leaf blades are 2 to 16 cm long, 1.5 to 5 mm wide, smooth to sparsely pubescent, folded or loosely rolled in the bud and sharply-pointed. The inflorescence consists of 3 to 7 spikes in a single whorl in a fingerlike arrangement and 3 to 10 cm long. In robust forms there may be up to 10 spikes, sometimes in two whorls. Spikelets are 2 to 3 mm long, in 2 rows tightly appressed to one side of the rachis; glumes are to ° the length of spikelet; lemma is boot-shaped, acute with fringe of hairs on the keel and longer than the glume; seed is 1.5 mm long, oval, straw to red-colored and free within the lemma and palea.
Bermudagrass has a fibrous, perennial root system with vigorous, deep rhizomes. Roots are produced at the nodes after new leaves or tillers are produced during the growing season and after new shoots are produced in the spring. Mature roots are yellow to brown while new roots are white. Mature roots deteriorate throughout the growing season and new roots are produced continuously. Root production and dieback has been reported to be particularly high in the spring at the onset of shoot production.
Adaptation and Use. Bermudagrass is a warm season perennial species
adapted to tropical and subtropical climates. It grows best under extended
periods of high temperatures, mild winters and moderate to high rainfall.
Temperature is the main environmental factor that limits its adaptability
to tropical and subtropical areas of the world. The northern limits of bermudagrass
extend into the transitional zone of the United States where low temperatures
seldom drop below 10°F. In general, temperatures below 30°F kill
the leaves and stems of bermudagrass. Research has demonstrated that bermudagrass
will continue to grow with night temperatures as low as 34°F if day
temperatures are near 70°F. However, when average temperatures drop
below 50°F growth stops and the grass begins to discolor. At the onset
of low temperatures in the fall and winter, bermudagrass begins to discolor,
protein fractions change in composition and reserve carbohydrates increase
in the stems and rhizomes. After the first killing frost, leaves and stems
of bermudagrass remain dormant until average daily temperatures rise above
50°F for several days. The roots and rhizomes of bermudagrass continue
to grow several weeks after the leaves and stems stop growth.In warm frost-free climates bermudagrass remains green throughout the year, but growth is significantly reduced at the onset of cool nights. The species makes the best growth where average daily temperatures are above 75°F. Optimum daytime temperature for bermudagrass is between 95° and 100°F.
Soil temperature, as influenced by air temperature, is also important to the growth and development of bermudagrass turf. Soil temperatures above 65°F are required for significant growth of rhizomes, roots and stolons. Optimum soil temperature for root growth is around 80°F.
Bermudagrass has a high light requirement and does not grow well under low light (shaded) conditions. The duration of the light period (day length) also influences growth and development of bermudagrass. Both increased light intensity and day length increase rhizome, stolon and leaf growth in bermudagrass. At low light intensities (less than 60% full sunlight) bermudagrass develops narrow, elongated leaves; thin upright stems; elongated internodes and weak rhizomes. Consequently, bermudagrass develops a very sparse turf under moderately shaded conditions.
Bermudagrass is found in tropical and subtropical climates with 25 to 100 inches of annual rainfall, but it also survives in arid climates along waterways and in irrigated areas. Where annual rainfall is below 20 inches per year, bermudagrass requires irrigation to survive. Bermudagrass develops into a semidormant state during very dry conditions, but has the capability of surviving extreme droughts. Rhizomes of bermudagrass can lose 50% or more of their weight and still recover when favorable moisture develops. Generally, common bermudagrass, or tetraploids of C. dactylon, have the deepest root and rhizome penetration and better withstand prolonged drought periods.
Common bermudagrass also has the characteristic of producing seedheads under stress conditions such as drought. Thus, the seeds provide another method by which the species can survive extreme drought. Some natural biotypes of C. dactylon produce numerous seeds. The seeds are very small with about 2,000,000 seeds per pound.
Bermudagrass grows well on a wide variety of soils from heavy clays to deep sands, provided fertility is not limiting. It tolerates both acid and alkaline soil conditions and is highly tolerant to saline conditions. Bermudagrass survives some flooding but does best on well-drained sites. Although it may persist under low fertility, bermudagrass has a high nitrogen requirement for good quality turf.
Bermudagrass has numerous turf uses. It has been suggested that if ever a plant deserved a monument for its service to mankind, it was bermudagrass for what it has done to prevent soil erosion, to stabilize ditch banks, roadsides and airfields, to beautify landscapes and to provide a smooth, resilient playing surface for sports fields and playgrounds. Bermudagrass also provides hay and pasture for livestock throughout the tropical and subtropical areas of the world.
Turf uses of common bermudagrass include sports fields, lawns, parks, playgrounds, golf course fairways, roadsides, cemeteries, and other general purpose turf. Hybrid bermudagrass and selections of common bermudagrass are used for special purposes such as sports fields, golf greens, bowling greens, tennis courts, and lawns.
Bermudagrass is well suited to high traffic areas such as sports fields, golf courses, and playgrounds. A dense bermudagrass turf tolerates moderate wear and compaction and recovers rapidly from wear injury. Under moderate fertilization, frequent mowing and adequate moisture bermudagrass forms a dense, fine-textured turf. The only situation where bermudagrass cannot be used is in moderate to heavily shaded sites.
Varieties. Selections of superior strains of common bermudagrass, natural hybrids between C. dactylon and C. transvaalensis and crosses resulting from grass breeding programs have been released by state universities, the Crop Research Division of the USDA and the U.S. Golf Association Green Section. All of the hybrid bermudagrasses are sterile and must be propagated by sprigs or sod. Some selections from C. dactylon produce viable seed. Nu-Mex Sahara and Princess bermudagrass are improved seeded varieties of bermudagrass. Brief descriptions of the major sports turf-type bermudagrass varieties follows:
U-3 (C. dactylon). Selected from Savannah Golf Club near Savannah, Georgia in 1936 from a series of fine-strain selections. Selected because of its cold hardiness, fine texture, rapid spread and durability under a wide range of soil and climatic conditions. The selection was released in 1957 by the Crops Research Division, ARS, USDA, and the U.S. Golf Association Green Section. Adapted for use on lawns, golf courses and athletic fields.
Sunturf (C. magennissii). Originated in S. Africa as a natural hybrid between C. dactylon and C. transvaalensis and introduced into the U.S. in 1949. Released cooperatively by Alabama, Arkansas, Oklahoma and South Carolina Agricultural Experiment Stations in 1956. Dark Green, fine-textured, low growing variety that forms a very dense turf. Widely used for lawns in the southwestern U.S.
Tiflawn (Cynodon sp.). A hybrid between two selections from a pasture breeding program at the Georgia Coastal Plains Experiment Station at Tifton. Released in 1952 by Georgia Agricultural Experiment Station and the Crops Research Division, ARS, USDA. A medium-textured, very fast spreading, wear resistant variety that forms a dense, weed-free turf. Particularly well-suited for lawns and athletic fields in the southeastern U.S.
Tifgreen (C. dactylon x C. transvaalensis). A hybrid between a fine- textured selection of C. dactylon from the Charlotte Country Club, Charlotte, North Carolina, and C. transvaalensis. Released in 1956 by Georgia Agricultural Experiment Station and Crop Research Division, ARS, USDA. Tifgreen in a low growing, rapid spreading variety that develops a dense, weed resistant turf. Its density, fine texture and soft leaves make Tifgreen an excellent turf for golf greens. Also, it tolerates overseeding with winter grasses better than most bermudagrass varieties. Tifgreen is highly susceptible to injury by ground pearls in the southwestern U.S. and is severely discolored by air pollution in areas where this is a problem. It is also highly susceptible to spring dead spot in the transition zone of the U.S. Tifgreen is recommended for golf greens and fairways, tennis courts, bowling greens and fine lawns with a high level of maintenance.
Texturf-10 (C. dactylon). Selected from common bermudagrass fairway at the Corsicana Country Club in Corsicana, Texas, for its medium texture, dark green color, sparse seedheads and dense turf. It also has good wear tolerance and late fall color retention and makes earlier spring recovery than common bermudagrass. Texturf-10 was released by the Texas Agricultural Experiment Station in 1957. It is recommended for athletic fields, playgrounds and lawns. Texturf-10 is sensitive to chlorinated hydrocarbon insecticides, turning a straw color several days after an application of these materials. The grass recovers in 7 to 10 days with no permanent damage.
Tifway (C. dactylon x C. transvaalensis). A chance hybrid that appeared in a lot of seed of C. transvaalensis from Johannesburg, South Africa, in 1954. It is very similar to Tifgreen except for its greater stiffness of leaf blades and darker green color. Released by the Georgia Agricultural Experiment Station and Crops Research Division, ARS, USDA, in 1960. Recommended for golf course tees and fairways, home lawns, athletic fields and tennis courts. An improved selection of Tifway, Tifway II, was recently released for its superior cold tolerance.
Santa Ana (C. dactylon x C. transvaalensis). A selection from C. dactylon (Royal Cape) obtained from South Africa in 1954. The initial selection was made at UCLA in 1956 for its deep blue-green color, medium-fine texture and good fall color retention. Santa Ana was found to have good salt tolerance and a high degree of tolerance to smog which frequently discolored Tifway and Tifgreen varieties. Released by the California Agricultural Experiment Station in 1966, Santa Ana is recommended for golf courses, athletic fields, playgrounds and lawns. Careful management is required to prevent thatch accumulation.
Ormond (C. dactylon). Selected from a fairway at Ellinor Village Country Club, Ormond Beach, Florida, for attractive blue-green color, vigor and prostrate growth habit. It has a medium texture and tolerance to leaf disease, but lacks cold tolerance. Released by Florida Agricultural Experiment Station in 1962. Well adapted in Florida for use on lawns, golf courses, playgrounds and athletic fields.
Midway (C. dactylon x C. transvaalensis). A medium-textured lawn grass that produces relatively few seedheads. Released by the Kansas Agricultural Experiment Station in 1965 for its superior cold tolerance in Kansas. Recommended for lawns, golf courses and athletic fields in the upper South.
Tifdwarf (C. dactylon x C. transvaalensis). A selection from Tifgreen golf greens in Sea Island, Georgia, and Florence, South Carolina, where both greens were planted with Tifgreen obtained from the Georgia Coastal Plain Experiment Station at Tifton. Evidence indicates that Tifdwarf is a vegetative mutant that occurred in Tifgreen at Tifton before the first planting stock was sent out for testing. Tifdwarf resembles Tifgreen except that its leaves and internodes are significantly shorter than those of Tifgreen and it has a darker green color. Tifdwarf turns a reddish-purple color after the first cool temperatures in the fall. High rates of nitrogen in the fall will reduce the degree of discoloration. Tifdwarf is slower to recover than Tifgreen when both are planted on 12-inch center. Released by the Georgia Agricultural Experiment Station, Tifton and Crop Research Division, ARS, USDA, in 1965 for its superior putting quality. Tifdwarf is recommended for golf greens, tennis courts and bowling greens.
Pee Dee (C. dactylon x C. transvaalensis). A selection from an early South Carolina planting of Tifgreen. Like Tifdwarf, Pee Dee is believed to be a mutation from Tifgreen. Pee Dee is a dark green, very fine (dwarf) textured, fast spreading variety. Unlike Tifdwarf, Pee Dee is faster spreading than Tifgreen when planted on equal spacings. Released by the South Carolina Agricultural Experiment Station, Clemson, in 1968. Recommended for golf greens in the southeastern United States.
Propagation. Common bermudagrass (C. dactylon (L) Pers.) is the only widely used turf-type bermudagrass variety that can be established from seed. Nu-Mex Sahara, Princess, Sonesta are new seeded varieties that have seen limited use in the southwestern U.S. All hybrid bermudagrasses are sterile and must be propagated vegetatively by stolons, rhizomes or sod.
Certified bermudagrass seed should be planted at a rate of ° to 1 pound of seed per 1,000 sq. ft. Spring and summer plantings should utilize hulled bermudagrass seed for faster germination. Late fall and winter plantings should be with unhulled bermudagrass seed to delay germination of a significant amount of the seed until more favorable conditions occur in the spring. Unhulled bermudagrass seed might be planted together with annual ryegrass in the fall to provide temporary cover and protection from soil erosion during winter months. Annual ryegrass will delay the development of a bermudagrass turf, but it may be needed for cover and protection.
When planting in the fall and winter on areas subject to severe erosion, wheat or rye can be drilled with unhulled bermudagrass seed. The wheat or rye will establish quickly and provide some cover during winter months. The small grains also provide less competition than ryegrass to seedling bermudagrass in late spring.
Bermudagrass sprigs or stolons for planting should be freshly harvested and protected from desiccation by wind and sun. Also, they should not be subject to excessive heating which occurs when moist planting material is tightly packed or covered for several days. Sprigs are usually distinguished from stolons in that sprigs consist of stolons with roots and rhizomes; whereas stolons consist of above ground parts only. Sprigs are produced by shredding harvested sod or by sprig harvesters. Stolons are generally harvested with a vertical mower or a flail mower set close to the ground. Sprigs will tolerate slightly more environmental stress during planting and establishment because of the energy reserves in the roots and rhizomes.
Sprigs or stolons should be planted at 5 to 15 bushels per 1,000 sq. ft. depending on the rate of cover required. Higher planting rates up to 25 or more bushels per 1,000 sq. ft. will provide a faster grass cover. A minimum planting rate should be 5 bushels per 1,000 sq. ft. or 200 bushels per acre. Sprigs or stolons should be broadcast on a clean seedbed and pressed into moist soil with a roller or covered lightly with soil or mulch. Moist conditions must be maintained for 2 to 3 weeks after planting to obtain a good cover.
Seed or sprigs should not be planted before soil temperature is above 65°F. Planting too early may retard development of a turf and extend the critical establishment period several weeks. Soil temperatures of 68°F to 75°F are ideal for germination and rapid development of bermudagrass.
Fertilizer, as determined by a soil test, should be incorporated into the soil during seedbed preparation. Nitrogen fertilizer can be applied to the soil surface immediately prior to planting or at the time of planting at a rate of 1 pound per 1,000 sq. ft. or 40 to 50 pounds per acre. Nitrogen should be applied 3 to 4 week intervals until a cover is obtained.
Mowing should begin several weeks after planting to control weed growth and promote spreading of bermudagrass. If additional weed control is needed selective post emergence herbicides can be applied 3 to 4 weeks after planting. Preemergence herbicides should not be applied to bermudagrass turf during the first growing season. Weed control will greatly enhance bermudagrass growth and coverage.
Management. Bermudagrasses, in general, are drought tolerant; that is, they survive dry soil conditions longer than most turfgrasses. However, drought tolerance in bermudagrass is based on their ability to become semidormant during severe droughts and to recover from stolons and rhizomes when moisture becomes available. The grass does not provide a desirable turf under drought conditions.
Bermudagrass does respond readily to irrigation. In general, water requirements of bermudagrass depends on turf use and climatic factors such as temperature, wind, humidity and light intensity. Water requirements increase with increasing levels of maintenance (golf green > sports field > lawn > roadside), higher temperatures, higher wind speed, lower humidity and greater light intensity. Of course, the longer the growing season the greater the water requirement for the year. Water use rates may range from less than 0.1 inch per day to 0.3 inch per day depending on these environmental conditions.
The frequency of irrigation is dependent on water use rate and soil type. Clay soils, for example, hold more water than sandy soils and, consequently, require less frequent irrigations. The depth of the rootzone also influences the frequency of irrigations. Bermudagrass roots can grow to a depth of six feet or more depending on soil profile characteristics. However, the majority of the root system, 80% or more, is found in the top 6 inches of soil. Where roots extend several feet into the soil, thorough and infrequent irrigation produces the most drought tolerant turf. Light, frequent irrigations such as practiced on golf greens produce shallow-rooted grass that shows drought stress very rapidly.
Bermudagrass does not tolerate poorly drained sites. On compacted sites and heavy clay soils, irrigation must be closely controlled to avoid waterlogged conditions. Hard, compacted sites can often be improved with respect to water penetration by core aeration and topdressing with sand or an aggregate material such as Turface. The presence of a heavy thatch layer will also interfere with water penetration. Thatch removal by vertical mowing and core aeration also improves water penetration and reduces the frequency of irrigation required.
Mowing requirements for bermudagrass turf are dependent on variety, use and the level of maintenance. Common bermudagrass and other medium textured varieties produce dense, wear tolerant turf when mowed at heights between ° and 1° inches. The lower heights being good for golf and sports turf and the tall heights for lawns. At mowing heights above 1° inches bermudagrass develops turf with an acceptable appearance but with poor wear tolerance. Fine-textured hybrid bermudagrasses such as Tifway should be mowed at a height of 1 inch or less. Taller mowing heights with these grasses produce puffy, stemmy turf that is easily scalped during mowing.
As a general recommendation to maintain good turf density and color, no more than 40% of the leaf tissue should be removed at any mowing. Thus, the shorter the mowing height, the more frequent the turf must be mowed. Golf greens mowed at 3/16-inch or less are mowed daily, sports fields mowed at ° inch are mowed at 3-day intervals and lawns mowed at 1 to 1° inches, at 5 to 7 day intervals.
Reel mowers produce the best cut on bermudagrass turf. However, the number of blades per cutting reel determines the smoothness of cut. Common bermudagrass mowed at 1 inch or higher can be cut with a reel with 5 or 6 blades. Common and hybrid bermudagrasses mowed at ° to 1 inch should be cut with a reel containing 7 blades. At heights below ° inch, 9 to 11 blades per reel are required for a smooth cut.
Bermudagrasses have a relatively high fertilizer requirement to maintain a high level of turf quality. The amount and frequency of fertilizer required depends on the desired appearance and growth rate of the turf, length of growing season, soil type, bermudagrass variety and the use of the turf. Where high quality is of critical importance and the turf is mowed frequently, 1 to 1.5 pounds of nitrogen per 1,000 sq. ft. per month may be applied during the growing season. The lowest rate of nitrogen that can be applied and still maintain acceptable bermudagrass turf for sports fields and golf courses is about 0.5 pounds of N per 1,000 sq. ft. per month.
Soil types also influence fertilizer needs. Sandy soils require light but frequent applications of nitrogen because of low nitrogen retention. Sandy soils are also typically low in other nutrients such as phosphorus and potassium and these nutrients must also be provided through fertilization. Soil tests are required to determine phosphorus, potassium, calcium and other nutrient deficiencies. Potassium is particularly important because of its contribution to root growth, environmental stress tolerance (heat, cold and drought) and wear tolerance. Potassium has also been found to reduce susceptibility of bermudagrass to leaf spot diseases.
Bermudagrass tolerates a wide range in soil reaction, but performs best between pH 6.5 and 8.0. At pH levels below 6.5 limestone should be added according to soil test recommendations.
Bermudagrass varieties also differ slightly in nitrogen requirements. Common bermudagrass and selections from common generally have a lower nitrogen requirement than the hybrid bermudagrasses. Tifgreen may have the highest requirement for nitrogen to maintain a dark green color and keep seed production to a minimum. Tifway bermudagrass, which has an inherent dark green color, requires less nitrogen than Tifgreen. Excessive nitrogen fertilization, beyond that required to maintain color and vigor, leads to increased mowing, irrigation, thatch control and pest problems all of which result in higher maintenance costs.
Turf use has a significant effect on the amount of fertilizer required. Golf greens, bowling greens and tennis courts have a very high nitrogen requirement; sports fields and golf course fairways, an intermediate requirement and lawns, and other low maintenance areas, a low nitrogen requirement.
Hybrid bermudagrasses require regular cultivation practices - vertical mowing, aeration and topdressing - to maintain high quality turf. Bermudagrass golf greens may require weekly vertical mowing and monthly topdressing under heavy use conditions. Sports fields and golf fairways may need these cultural operations on an annual basis. Without cultivation bermudagrass turf tends to develop thatch, grain and spongy conditions that result in scalping and a nonuniform appearance.
Common bermudagrass and selections from common need less cultivation to prevent thatchy conditions. However, under heavy use common bermudagrass needs regular aeration and topdressing to prevent compaction and maintain turf quality.
Pest Problems. Bermudagrass tolerates a wide range of environmental conditions and survives in nature where fertility and rainfall are adequate and winter temperatures are not too low. Bermudagrass does have numerous pest problems, however, which tend to increase with higher levels of management. High nitrogen fertilization rates, close mowing and frequent irrigation tend to increase the susceptibility of bermudagrass to insects and diseases.
Serious insect pests that feed on the foliage of bermudagrass include armyworms, cutworms, sod webworms, bermudagrass mites and Rhodegrass scale (mealybug). The latter two insects cause damage by sucking juices from the stems and stunting normal growth of the grass. White grubs can severely damage bermudagrass by feeding on grass roots. Nuisance type insects found on bermudagrass include chiggers, ants and ticks.
Insect control on bermudagrass should include cultural, biological and chemical methods. Under good management bermudagrass can tolerate low populations of most of these insects. Where insect populations are high enough to cause significant damage, biological and chemical methods may be required. Some species of white grub can be controlled with milky spore disease, a biological control that effectively controls white grub populations. Baccilus thuringensis is a biological control for armyworms, cutworms and sod webworms. And, Neodusmetia sangwai, a fly-like parasite, has effectively eliminated the Rhodegrass mealybug in Texas. Where these biological controls are not effective, chemicals can be used together with these cultural and biological controls to reduce insect populations to an acceptable level.
Several serious disease organisms and nematodes also attack bermudagrass turf. Dollar spot, spring dead spot, leaf spot, brownpatch and Pythium are all fungus diseases that attack bermudagrass turf. Several species of nematodes also cause significant damage to bermudagrass turf.
As in the case of insects, cultural and chemical methods may be required to control disease and nematode problems. High nitrogen fertilization rates should be avoided during peak periods of disease attacks. Thatch should be controlled through proper mowing and cultivation. And, water should be applied properly to avoid severe drought stress or waterlogged conditions which increases the susceptibility of grass to some diseases.
Where cultural practices do not adequately control turf diseases, fungicides are available for control. In some intensive maintenance situations, preventive applications of fungicides provide the best means of disease control.
Weeds are also serious pests in bermudagrass turf. Vigorous, healthy turf properly maintained provides the best means of weed control in bermudagrass turf. But, where turf thins due to environmental stress, pest problems or poor management, weeds rapidly invade bermudagrass.
Broadleaved weeds including clover, chickweed, dandelion, henbit, dichondra and others can be controlled with the hormone type herbicides such as 2,4-D, MCPP, dicamba. Grassy weeds including crabgrass and dallisgrass can be controlled with several applications of MSMA in spring or early summer. Annual grasses including crabgrass and annual bluegrass can be controlled with preemergence herbicides. However, all of these herbicides must be used together with good management to effectively reduce weed populations.