17.44   CYNODON Rich.
Mary E. Barkworth

Plants perennial; sometimes stoloniferous, sometimes also rhizomatous, often forming dense turf. Culms 4-100 cm. Sheaths open; auricles absent; ligules of hairs or membranous; blades flat, conduplicate, convolute, or involute, sometimes disarticulating. Inflorescences terminal, digitate or subdigitate panicles of spikelike branches; branches (1)2-20, 1-sided, with 2 rows of solitary, subsessile, appressed, imbricate spikelets. Spikelets laterally compressed, with 1(-3) florets, only the lowest floret functional; rachilla extension usually present, sometimes terminating in a reduced floret; disarticulation above the glumes. Glumes usually shorter than the lemmas, membranous, keeled, usually muticous; lower glumes 1-veined; upper glumes 1-3-veined, occasionally shortly awned; lemmas membranous to cartilaginous, 3-veined, keeled, keels with hairs, occasionally winged, apices mucronate or muticous; paleas about as long as the lemmas, 2-keeled; anthers 3; style branches 2, plumose; lodicules 2. x = 9. Name from the Greek kyon, dog, and odous, tooth, a reference to the sharp, hard scales of the rhizome.

Cynodon is a genus of nine species, all of which are native to tropical regions of the Eastern Hemisphere. Several species are used as lawn and forage grasses in tropical and warm-temperate regions. The most widespread species, C. dactylon, is also the most frequently encountered species in the Flora region. It is used for lawns, putting greens, and pastures in southern portions of the region, but is generally considered a weed in other parts.

The status of several species in the Flora region is unclear. Species other than C. dactylon usually grow only under cultivation, but there are scattered records of populations of other species from the southern United States that appear to have become established. Cultivars of C. aethiopicus and C. nlemfuënsis are used for pasture primarily in tropical Florida. Cynodon transvaalensis has had limited commercial distribution as a turf grass.

Many cultivars of Cynodon have been developed, some from hybrids between it and other species such as C. transvaalensis, C. aethiopicus, and C. nlemfuënsis. The cultivars may exhibit combinations of features that are not found in the wild species, making it difficult to accommodate them in a key.


SELECTED REFERENCES Alderson, J. and W.C. Sharp. 1995. Grass Varieties in the United States. CRC Press, Boca Raton, Florida, U.S.A. 296 pp. [previously published by the Soil Conservation Service, U.S. Department of Agriculture, as Agricultural Handbook No. 170, revised 1994]; Assafa, S., C.M. Taliaferro, M.P. Anderson, B.G. de los Reyes, and R.M. Edwards. 1999. Diversity among Cynodon accessions and taxa based on DNA amplification fingerprinting. Genome 42:465-474; Busey, P. and S. Boyer. 2002. Bermudagrass speeds: Can fast greens be green? http://www.floridaturf.com/ballroll.htm; Caro, J.A. and E.A. Sánchez. 1969. Las especies de Cynodon (Gramineae) de la República Argentina. Kurtziana 5:191-252; de Wet, J.M.J. and J.R. Harlan. 1970. Biosystematics of Cynodon L.C. Rich. (Gramineae). Taxon 19:565-569; Harlan, J.R. and J.M.J. de Wet. 1969. Sources of variation in Cynodon dactylon (L.) Pers. Crop Sci. (Madison) 9:774-778; Harlan, J.R., J.M.J. de Wet, W.W. Huffine, and J.R. Deakin. 1970. A guide to the species of Cynodon (Gramineae). Oklahoma Agric. Exp. Sta. Bull. B-673:1-37; Hitchcock, A.S. 1951 [title page 1950]. Manual of the Grassesof the United States, ed. 2, rev. A. Chase. U.S.D.A. Miscellaneous Publication No. 200. U.S. Government Printing Office, Washington, D.C., U.S.A. 1051 pp.; Jones, S.D. and G.D. Jones. 1992. Cynodon nlemfuënsis, (Poaceae: Chlorideae) previously unreported in Texas. Phytologia 72:93-95.

1
Lemma keels winged; panicle branches with flattened axes (subg. Pterolemma) ..... 7. C. incompletus
Lemma keels not winged; panicle branches with triquetrous axes (subg. Cynodon) (2)
2
Glumes 0.1-0.6 mm long ..... 1. C. plectostachyus
Glumes 1.1-2.6 mm long (3)
3
Panicles with 1-3(4) branches; culms 5-30 cm tall; blades 1-1.5 mm wide ..... 2. C. transvaalensis
Panicles with (2)4-20 branches; culms 5-100 cm tall; blades (1)2-7 mm wide (4)
4
Panicles with 2-6(9) branches in a single whorl; culms 5-40(50) cm tall (5)
Panicles with 4-20 branches in 1-5 whorls; culms 20-100 cm tall (6)
5
Panicles with (2)4-6(9) branches; anthers dehiscent at maturity ..... 3. C. dactylon
Panicles with 2-4 branches; anthers indehiscent at maturity ..... 4. C. ×magennisii
6
Lemma keels glabrous or with a few scattered hairs; panicle branches usually in 2-5 whorls, stiff, frequently red or purple; culms 25-100 cm tall, woody ..... 5. C. aethiopicus
Lemma keels shortly pubescent; panicle branches usually in 1 whorl, lax, usually green; culms 20-60 cm tall, not woody ..... 6. C. nlemfuënsis


1.   Cynodon plectostachyus (K. Schum.) Pilg.
Stargrass

Plants stoloniferous, not rhizomatous; stolons to 2 mm thick, arching. Culms 60-100 cm tall, 1-4 mm thick, glabrous. Sheaths mostly glabrous or sparsely to densely pilose, with long hairs adjacent to the ligules; ligules 1-2 mm; blades to 30 cm long, 4-8 mm wide, both surfaces scabrous and densely pubescent. Panicles with 6-20 subdigitate branches; branches 3-10 cm, in (1)2-7 closely spaced whorls, axes triquetrous. Spikelets 2.5-3 mm, closely imbricate; rachillas prolonged, glabrous, sometimes terminating in a vestigial floret. Lower glumes 0.1-0.3 mm; upper glumes 0.4-0.6 mm; lemmas 2.4-3 mm, keels not winged, keels and margins pubescent, hairs 0.3-0.4 mm; paleas stiffly ciliate on the keels. 2n = 18, 36.

Cynodon plectostachyus is native to tropical Africa. Its status in the Flora region is unclear. The records shown are from non-cultivated plants, but it is not known whether they represent established populations. Cynodon plectostachyus is not frost-tolerant.


2.   Cynodon transvaalensis Burtt Davy
African Dogstooth Grass, Floridagrass

Plants stoloniferous and rhizomatous; stolons slender, prostrate; rhizomes slender. Culms 5-30 cm tall, to 0.4 mm thick. Sheaths glabrous or with scattered hairs; ligules to 0.3 mm, membranous and ciliolate; blades to 4 cm long, 1-1.5 mm wide, flat or involute and filiform, both surfaces pubescent. Panicles with 1-3(4) branches; branches 0.7-2.1 cm, in a single whorl, reflexed at maturity, axes triquetrous. Spikelets 2-2.7 mm. Lower glumes 1.2-1.4 mm; upper glumes 1.1-1.3 mm; lemmas 2.2-2.7 mm, keels not winged, stiffly and sparsely pubescent, margins glabrous or hispidulous; paleas glabrous. 2n = 18.

Cynodon transvaalensis is native to southern Africa. Hitchcock (1951, p. 504) reported that it was coming into cultivation as a lawn grass, but it is no longer sold in the Flora region, nor is there any evidence that earlier plantings have led to its establishment. Strains tested in Florida for use in putting greens were unable to withstand the mowing and moisture conditions used to maintain such areas (Busey and Boyer 2002). Strains of the species have, however, been crossed with strains of C. dactylon and cultivars developed from these crosses are sometimes used as turf grasses in the southern United States and in similar climates throughout the world.


3.   Cynodon dactylon (L.) Pers.
Bermudagrass

Plants stoloniferous, usually also rhizomatous. Culms 5-40(50) cm, not becoming woody. Sheaths glabrous or with scattered hairs; collars usually with long hairs, particularly at the margins; ligules about 0.5 mm, of hairs; blades 1-6(16) cm long, (1)2-4(5) mm wide, flat at maturity, conduplicate or convolute in bud, glabrous or the adaxial surfaces pilose. Panicles with (2)4-6(9) branches; branches 2-6 cm, in a single whorl, axes triquetrous. Spikelets 2-3.2 mm. Lower glumes 1.5-2 mm; upper glumes 1.4-2.3 mm; lemmas 1.9-3.1 mm, keels not winged, pubescent, margins usually less densely pubescent; anthers dehiscent at maturity; paleas glabrous. 2n = 18, 36.

Cynodon dactylon is a variable species, but taxonomists disagree on just how variable. Caro and Sánchez (1969) limited C. dactylon to plants with conduplicate leaves, placing those with convolute leaves in a number of other species, such as C. affinis Caro & Sánchez and C. aristiglumis Caro & Sánchez; de Wet and Harlan (1970) do not mention this character in their study of Cynodon. Caro and Sánchez also employed several other characters in the key separating C. dactylon from the species with convolute immature leaves, but the overlap between the two sides of the lead is substantial. Pending further study, the broader interpretation, in which C. dactylon includes plants with both convolute and conduplicate leaves, has been adopted.

Several varieties of C. dactylon have been described, in addition to which numerous cultivars have been developed, some as turf grasses for lawns or putting greens, others as pasture or forage grasses. Their useful range is limited because C. dactylon is not cold hardy, going dormant and turning brown when nighttime temperatures fall below freezing or average daytime temperatures are below 10° C.

The most commonly encountered variety, both in the Flora region and in other parts of the world, is C. dactylon var. dactylon, largely because it thrives in severely disturbed, exposed sites; it does not invade natural grasslands or forests. Determining how many other varieties are established in the Flora region is almost impossible, because there has been no global study of variation in the species. The presence of numerous cultivars complicates an already difficult problem. The two varieties keyed out below are the only two that grow in the Flora region according to de Wet and Harlan (1970), but these authors do not appear to have considered the taxa recognized by Caro and Sánchez (1969). For most purposes, it is probably neither necessary nor feasible to identify the variety of C. dactylon encountered.

Cynodon dactylon is considered a weed in many countries and it is true that, once established, it is difficult to eradicate. It does, however, have some redeeming values. It is rich in vitamin C, and its leaves are sometimes used for an herbal tea. It is claimed to have various medicinal properties, but these have not been verified. It is considered a good pasture grass, in addition to which it is sometimes grown as an ornamental and for erosion control on exposed soils.

1
Rhizomes near the surface (sometimes surfacing for a short distance before submerging again), the tips eventually surfacing and, like the lateral buds, producing tillers ..... var. dactylon
Rhizomes growing up to 1 m deep, the tips remaining below ground, only the lateral buds producing tillers ..... var. aridus


Cynodon dactylon var. aridus J.R. Harlan & de Wet

A cultivar of this variety, 'Giant', has been introduced to the Yuma region of Arizona (Harlan et al. 1970).


Cynodon dactylon (L.) Pers. var. dactylon

As noted above, this is by far the most common variety of Cynodon dactylon.


4.   Cynodon ×magennisii Hurcombe
Magennis' Dogstooth Grass

Plants stoloniferous and rhizomatous. Culms to 20 cm. Ligules of hairs; blades 1-1.5 mm wide, pubescent, at least adaxially. Panicles with 2-4 branches; branches in a single whorl, axes triquetrous. Spikelets about 3 mm. Glumes about 2 mm, about 2/3 as long as the spikelets; lemma keels not winged; anthers indehiscent at maturity. 2n = 27.

Cynodon ×magennisii is a natural triploid hybrid between C. dactylon and C. transvaalensis (Harlan et al. 1970). Several cultivars have been developed for lawns and golf courses in the southern United States. These exhibit differing mixes of the characteristics of the two parent species.

Like triploid cultivars of C. dactylon, C. ×magennisii fails to produce either pollen or seeds and its anthers remain narrow and indehiscent at maturity. Diploid and tetraploid plants of C. dactylon also frequently fail to set seed because they are highly self-sterile, but they produce good pollen and their anthers dehisce at maturity.


5.   Cynodon aethiopicus Clayton & J.R. Harlan
Ethiopian Dogstooth Grass

Plants stoloniferous, not rhizomatous; stolons stout, woody, lying flat on the ground. Culms 25-100 cm tall, 2-6 mm thick, becoming woody. Sheaths glabrous; ligules about 0.3 mm, membranous, ciliolate; blades 3-25 cm long, 3-7 mm wide, glabrous or sparsely pubescent, glaucous. Panicles with 4-10(20) branches; branches 3.5-7 cm, in (1)2-5 whorls, stiff, usually red or purple, axes triquetrous. Spikelets 2-3 mm. Glumes equaling to slightly exceeding the florets; lower glumes 2-2.2 mm; upper glumes 1.7-2.6 mm; lemmas 2.1-2.6 mm, keels not winged, glabrous or with a few scattered hairs. 2n = 18, 36.

Cynodon aethiopicus is native to the East African rift. It is now established along the canal bank in the Santa Ana National Wildlife Refuge in Texas, and is expected to spread. The cultivar 'McCaleb' has been released as a forage grass for use in Florida.


6.   Cynodon nlemfuënsis Vanderyst
African Bermudagrass

Plants stoloniferous, not rhizomatous; stolons stout, woody, usually lying flat on the ground. Culms 20-60 cm tall, 1-5 mm thick, not becoming woody. Sheaths glabrous; ligules about 0.3 mm, membranous, ciliolate; blades 5-16 cm long, 2-6 mm wide, abaxial surfaces glabrous or with scattered long hairs, adaxial surfaces with scattered long hairs. Panicles with 4-13 branches; branches (2)4-7(10) cm, in 1(-3) whorls, lax, usually green, axes triquetrous. Spikelets 2-3 mm. Lower glumes 1.7-2 mm; upper glumes 1.5-2.3(3) mm; lemmas 1.9-2.9 mm, keels not winged, shortly pubescent, at least distally; paleas glabrous. 2n = 18, 36.

Cynodon nlemfuënsis is native to east and central Africa, but it is now established in southern Texas (Jones and Jones 1992), and may be present in other parts of the southern United States. It is similar to C. dactylon, but differs in being larger and lacking rhizomes. It is also less hardy, not becoming established where temperatures fall below -4° C. Plants in the Flora region belong to Cynodon nlemfuënsis Vanderyst var. nlemfuënsis, which differs from C. nlemfuënsis var. robustus Clayton & J.R Harlan in having shorter inflorescence branches (2-7(10) cm rather than 6-10 cm) and thinner culms (1-1.5 mm rather than 2-5 mm). Cultivars of C. nlemfuënsis include 'Florico', 'Florona', 'Ona', and 'Costa Rica'.


7.   Cynodon incompletus Nees

Plants stoloniferous, not rhizomatous. Culms 5-30 cm. Sheaths glabrous; ligules membranous; blades 1.5-6 cm long, 2-4 mm wide, glabrous or pubescent. Panicles with 2-6 branches; branches 2-5 cm, in a single whorl, axes flattened. Spikelets 2-3 mm, narrowly to broadly ovate. Glumes 1.7-2.1 mm, exceeded by the florets; lemmas 2.2-2.6 mm, keels winged and pubescent, margins glabrous. 2n = 18, 36.

Cynodon incompletus is native to southern Africa. A hybrid between the two varieties identified below, Cynodon ×bradleyi Stent, is used as a lawn grass in North America (de Wet and Harlan 1970).

1
Blades glabrous or sparsely hirsute; spikelets 2.5-3 mm long, narrowly ovate ..... var. incompletus
Blades densely hirsute; spikelets 2-2.5 mm long, broadly ovate ..... var. hirsutus