The newest cold-tolerant bermudagrass putting greens

At Oklahoma State University, researchers are developing hybrid bermudagrasses for putting greens that have improved cold temperature tolerance. The susceptibility of bermudagrass hybrids (Cynodon spp.) to winter injury in the transition zone is a significant concern.

Mike Kenna, Ph. D.

Hybrid bermudagrass putting greens may help superintendents in the transition zone focus on peak season, putting green playability in the summer rather than on its survival during the summer months. Current ultradwarf cultivars are susceptible to winter injury. Protective covers reduce winter injury, but significant labor costs are associated with covering and uncovering greens.

The objectives of their recent studies were to evaluate five golf course putting green-type experimental genotypes (OKC6318, OKC0805, OKC1609, OKC0920 and OKC3920) and three commercially available bermudagrasses (Champion Dwarf, Tifeagle and Tahoma 31) for freeze tolerance by subjecting them to 11 freezing temperatures ( 25 to 7 degrees F) under controlled growth chamber conditions.

We conducted experiments in batches, with four genotypes per batch, and each batch replicated in time. The mean lethal temperature to kill 50 percent of the population (LT₅₀) for each genotype was determined. There were significant differences in LT₅₀ values among the bermudagrass genotypes. ‘Champion Dwarf’ had an LT₅₀ value ranging from 23 to 22 degrees F across all three batches.

The experimental genotypes tested in this study had LT₅₀ values ranging from 19 to 17 degrees F and were each lower than that of Champion Dwarf, Tahoma 31, the top performing genotype, had an LT₅₀ value ranging from 18 to 16 degrees F across all three batches.

OKC 3920 was the only experimental genotype with an LT₅₀ value in the same statistical group as Tahoma 31. OKC3920, targeted for use on putting greens, shows improved freeze tolerance that is significantly better than the current ultradwarf cultivars.