Relations between low temperature tolerance and color changes in fall and spring seasons of zoysiagrass (Zoysia japonica Steud.)

Zoysiagrass (Zoysia spp.) is warm season grass used for lawns, golf courses and athletic fields. Although it has better low temperature tolerance compared to other warm season grasses, its longer dormant period than cool season grasses prevents its wide usage in transitional and cooler climate zones. This study analyzed the relationships among low temperature tolerance, green color changes during the fall and spring and the dormant period length among seven Zoysia japonica Steud. cultivars and accessions: two cultivars, four Chinese accessions and one Japanese accession. A relationship between low temperature tolerance and color changes due to dormancy and re-greening up was examined. Plant samples from the tested Z. japonica were cooled to between −8 and −16°C to measure the lethal temperatures at which 50% of plants died (LT50). These LT50 ranged from −7.3 to −10.1°C, with Lanyin No. 3 having the poorest low temperature tolerance. In the field, the color changes from green to brown for the whole plant in the fall and from brown to green in the spring occurred within 15–20 days as determined by digital analysis from fall 2008 to spring 2010. The fall colors changes (going dormant) on November 8, 2008 and November 7, 2009 were positively correlated with the LT50 (r = 0.824 and 0.823, respectively). The spring colors changes (green-up) on April 24, 2009 and May 19, 2010 were negatively correlated with the LT50 in both 2009 (r = −0.878) and 2010 (r = −0.869). The dormant period length in 2008–2009 was positively correlated (r = 0.765) with the LT50. This study demonstrated that Z. japonica with poor low temperature tolerance has better green‬‬ retention in the fall but less green color in the spring‬‬. Furthermore, Z. japonica, which became dormant later underwent green up later and had a longer dormant period, mainly due to slower green up in spring.‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬