Extreme cold temperature conditions persisting for days, weeks and even months are nothing but normal to many parts of Canada during the winter months. When the mercury dips below freezing, the turfgrass plant is exposed to many extremes that can cause damage. These freezing conditions cause damage, and Direct Low Temperature Kill is what this is known as.
The turfgrass plant in large part is comprised of water and when freezing temperatures occur, the water freezes forming ice crystals inside the turfgrass plant ultimately causing the damage. Direct low temperature kill is most commonly a result when rapid drops in temperature occur, or when extreme cold temperatures persist. Several factors can affect direct low temperature kill including: the susceptibility of the turfgrass species, plant hardiness, rapidness of freezing, the number of times the plant freezes, and the rate of thawing.
Although there is no exact direct low temperature kill measurement or way to determine if, when, and how bad the damage could be, plant hardiness as it relates to turfgrass species tells us more about which species are more susceptible. Creeping Bentgrass, and Kentucky Bluegrass are regarded as having very good plant hardiness whereas perennial ryegrass and fine fescue have poor plant hardiness in which case low temperature kill damage is a lot more apparent on these species.