Longer Exposure Durations Increase Freeze Damage to Turf Bermudagrasses

Abstract

Bermudagrasses, Cynodon sp, are susceptible to winter injury in the transition zone for warm‐ and cool‐season turfgrasses. Our objectives were to determine relative freeze tolerance of recently released and standard cultivars using laboratory‐based methodology, and to determine the effect of extended exposure duration on survival. Plants were clonally propagated, then established and acclimated in growth chambers before exposure to a range of temperatures in a freeze chamber. ‘Tifway’ and ‘TifSport’ (−7.9°C) were significantly hardier than ‘Princess’ (−6.9°C), but less freeze tolerant than ‘U‐3’ (−8.9°C), ‘Patriot’ (−9.7°C), and ‘Midlawn’ (−10.3°C). Riviera (−8.3°C) was significantly hardier than Princess, but less freeze tolerant than Patriot and Midlawn. In a second set of experiments, acclimated plants were held at constant, subfreezing temperatures for various periods of time in a refrigerated bath. Survival of U‐3 and Riviera decreased to 25% or less when exposed to −7.0°C for 2 or 5 d, compared with 100 and 83% survival, respectively, when plants were removed from the bath immediately after equilibrating at −7.0°C. Princess exhibited 89% survival when removed immediately after equilibrating at −5.4°C, but survival after 2, 24, and 72 h was 67, 30, and 11%, respectively. Although minimum exposure temperature is a primary determinant of survival, freeze damage to turf bermudagrasses increased as exposure duration increased.