Freeze Tolerance Differences and Impact of Late Season Nitrogen and PGRs On Warm-Season Putting Green Species.

A relative lack of cold hardiness and early onset of dormancy are deterrents to widespread use of warm-season turfgrass species for putting greens in the transition zone.  Few studies have been conducted to determine the minimum temperatures at which warm-season putting green species can survive.  Additionally, limited information is available regarding the role of nitrogen fertility and plant growth regulators (PGRs) in prolonging green color in the fall and enhancing winter survival.  As such, this study was conducted to determine the freeze tolerance of four warm-season cultivars for putting green use in the transition zone and assess the impacts of late-season nitrogen and PGR applications on fall color retention and winter survival on those same cultivars.  This study was conducted in a cold stress simulator and in the field in Knoxville, TN.  ‘Champion’ and ‘TifEagle’ bermudagrass (Cynodon dactylon ´ traansvalensis Burtt-Davy), ‘SeaDwarf” seashore paspalum (Paspalum vaginatum), and ‘Diamond’ zoysiagrass (Zoysia matrella) were established in cone-tainers and on a sand-based rootzone.  In the field, final Nitrogen applications for the season were made on 15 August, 15 September, and 15 October, with and without monthly trinexepac-ethyl applications.  In the cold chamber, ‘Diamond’ zoysiagrass was more cold hardy than both ‘Champion’ bermudagrass and ‘SeaDwarf’ seashore paspalum, but was not different than ‘TifEagle’ bermudagrass.  In the field, later N applications prolonged turf color in the fall and hastened greenup in the spring for all varieities except ‘Diamond’ Zoysiagrass.