Freezing Tolerance of Six Cultivars of Buffalograss

Freezing tolerance is an important trait that determines geographical adaptation of a turfgrass. This study was conducted to assess the relative freezing tolerance, seasonal changes in freezing tolerance (LT50), and winter survival of six cultivars of buffalograss [Buchloë dactyloides (Nutt.) Engelm.]. The cultivars 91‐118, Tatanka, Texoka, Stampede, UCR‐95, and 609 were grown in the field at Fort Collins, CO. From September 1998 to April 1999 and from October 1999 to May 2000, stolons were sampled monthly from each plot and subjected to laboratory freezing tests. Survival and recovery following the freezing test indicated that all cultivars had similar LT50 in September and gradually increased in winter hardiness during fall. However, the capacity to acclimate and the maximum freezing tolerance were significantly different among the cultivars. Ranking of grasses for mean LT50 (°C) was Tatanka (−18.1) = 91‐118 (−18.0) ≤ Texoka (−17.1) < 609 (−14.4) < Stampede (−12.4) < UCR‐95 (−9.2) during midwinter in 1998‐1999 and Texoka (−21.7) = 91‐118 (−21.6) = Tatanka (−21.0) < 609 (−15.8) = Stampede (−15.1) < UCR‐95 (−14.0) during midwinter in 1999‐2000. Following freezing treatments, Tatanka and 91‐118 maintained a higher relative shoot and root regrowth than other cultivars. Root regrowth was reduced by freezing to a greater extent than shoot regrowth for all cultivars. Field winter survival, a measure of winter hardiness, in 1998, 1999, and 2000 was generally in agreement with laboratory test results, showing that Stampede, 609, and UCR‐95 were more susceptible to winterkill than 91‐118 and Tatanka. The differences in freezing tolerance among the cultivars tested indicates substantial intraspecific variation that may be used for breeding improvement.