Hybrid bermudagrass response to fall-applied trinexapac-ethyl and cool-season turfgrass overseeding

Hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) is a perennial warm-season (C4) turfgrass that enters winter dormancy, resulting in loss of green color and reduced visual quality. Maintaining acceptable turf performance during this period remains a major management challenge under Mediterranean climatic conditions. This study evaluated the effectiveness of overseeding hybrid bermudagrass with selected cool-season (C3) turfgrass species and cultivars, in combination with trinexapac-ethyl (TE) application, to sustain turf quality, photosynthetic activity, and surface greenness during winter dormancy and the subsequent spring transition. Field experiments were conducted from October 2023 to May 2024 at Akdeniz University using five cool-season cultivars belonging to Lolium perenne L., Poa pratensis L. and Festuca arundinacea Schreb. under TE-treated and non-treated conditions. Turfgrass quality, normalized difference vegetation index (NDVI), relative chlorophyll content and percentage of green turf cover were evaluated throughout the winter and spring periods. Results indicated that all overseeded plots exhibited significantly higher turf quality, NDVI, relative chlorophyll content and green cover compared with non-overseeded control plots. Significant differences were observed among species and cultivars, with L. perenne ‘Peri’ consistently demonstrating superior performance across all measured parameters. While fall-applied TE had limited effects during winter, it enhanced the spring transition of hybrid bermudagrass. These findings demonstrate that species and cultivar selection play a critical role in overseeding success and that TE application can be strategically used to improve spring transition dynamics.