COLD HARDINESS AND ICE TOLERANCE OF PASTURE GRASSES GROWN AND TESTED IN CONTROLLED ENVIRONMENTS

A number of forage grass species were tested for cold hardiness and ice tolerance after growth and cold hardening under controlled conditions. Tests exposing cold-hardened plants to a single level of stress separated species into statistically similar groups but, in a number of cases, the stress was not sufficient to kill plants so the true cultivar rankings were obscured. Derivation of the 50% kill point from a wide range of levels of stress served to identify cold hardiness and ice tolerance levels of cultivars of 10 species. Ranked according to the most hardy cultivar of the species tested were: timothy (Phleum pratense L.), Kentucky bluegrass (Poa pratensis L.), meadow foxtail (Alopecurus pratensis L.), red fescue (Festuca rubra L.), meadow fescue (Festuca pratensis L.), tufted hairgrass (Deschampsia caespitosa L.), creeping foxtail (Alopecurus arundinaceus L.), berings hairgrass (Deschampsia beringensis L.), orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinaceae). LT 50 values varied from −15.7 °C for timothy to −4.7 °C for reed canarygrass. Cold hardiness and ice tolerance were only loosely associated (r = 0.36). The most ice-tolerant species were berings and tufted hairgrasses and timothy with LI 50 values of 50, 39 and 44 d, respectively.Key words: Acclimation, encasement, freezing, resistance