Zoysiagrass Species and Genotypes Differ in Their Winter Injury and Freeze Tolerance

Lack of cold hardiness may limit widespread use of newly released zoysiagrass ( Zoysia spp.) cultivars in the transition zone. Our objectives were to quantify differences in the winter injury of 35 zoysiagrass genotypes in field plots in West Lafayette, IN, and the freeze tolerance of 13 genotypes in a cold stress simulator as well as determine the relationship between leaf width, establishment rate, and autumn growth with winter injury. Winter injury varied between years and among genotypes in the field study. Zoysia japonica Steud. genotypes had less winter injury each year than Z. matrella (L.) Merr. genotypes. Genotypes of Z. japonica available as seed had less winter injury (2% in both years) than genotypes of Z. japonica (41%, 2005; 54%, 2006) and Z. matrella (51%, 2005; 73%, 2006) available only as vegetative propagules. ‘Meyer’, ‘Chinese Common’, and ‘Zenith’ were the commercially available cultivars exhibiting the least winter injury (<7%) in both years, whereas ‘Victoria’, ‘DeAnza’, ‘Diamond’, and ‘Empress’ had the most winter injury (>88%) both years. There was a relationship ( r 2 = 0.48, P = 0.0088) between freeze tolerance (LT 50 ) in the cold stress simulator and winter injury in the field. Freeze tolerance ranged from −8.4°C (Diamond) to −11.5°C (Meyer and Zenith). Meyer has been the industry standard for zoysiagrass, but our research has identified other commercially available cultivars and genotypes with winter injury similar to Meyer.