Moving warm-season forage bermudagrass (Cynodon spp.) into temperate regions of North America

Georgia, located in the Southeastern USA, has been historically dominated by two perennial forage grass production systems. Tall fescue (Lolium arundinaceum [Schreb.] S.J. Darbyshire) is more prevalent in the northern parts of the state, while bermudagrass [Cynodon dactylon (L.) Pers.] is ubiquitous to the southern portion. Climatologists have documented notable changes in temperature and precipitation patterns in the state that have contributed to an invasion of warm-season species in the northern portion of the state. In the transition zones between warm-season and-cool-season perennial grass-dominated regions of North America, C4 grasses can maintain productivity at high temperatures while C3 grasses are transitioning to a reproductive stage with minimal vegetative growth during summer. For this reason, warm-season grasses could replace a portion of the grasslands at latitudes greater than 35 degrees. This manuscript documents the expansion of warm-season bermudagrass into northern Georgia, explores the climatic factors driving this transition, and highlights previous and on-going research. We specifically focus on evaluating freeze or cold tolerance of bermudagrass germplasm. The C. dactylon cultivars exhibit more cold tolerance than C. nlemfuensis (stargrass) since they are more rhizomatous and rely less on above-ground stolons for regrowth and winter survival. Conversely, these cultivars tend to have poor nutritive value and are highly susceptible to insect damage. On-going research is identifying germplasm that provides adequate cold tolerance to meet the needs of farmers transitioning to warm-season production systems in the lower transition zone.