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Direct low temperature kill on a new stand of perennial ryegrass.

Turfgrasses can sometimes be damaged by a phenomenon known as direct low temperature kill. This type of winterkill occurs during extremely cold temperatures early in the winter following a relatively warm period in late fall. Typically, plant tissues undergo a dehydration process in late fall in response to gradually decreasing temperatures and shorter photoperiods. The dehydration process is accompanied by an increase is cellular solutes (potassium ions, sugars, etc.), allowing the plants to “harden off” or tolerate freezing temperatures. Warm weather during late fall can delay the hardening process and allow plants to become susceptible to ice formation in crown tissues with the advent of a sudden and dramatic drop in temperatures.