Frost damage to small grains is highly dependant on the stage of the crop, the temperature and duration of the low temperature, and environmental conditions that existed before the frost occurred. Small grains are among the most frost tolerant of crops. When temperatures fall below 50 o F for several days before a frost, the crop goes through a hardening process and develops more tolerance. Drought stress can also cause hardening. Up to jointing small grains can easily withstand temperatures of 25 o F. After jointing the growing point moves above the soil surface and is more susceptible to frost damage.
Small grains are most susceptible to frost from the late boot through flowering.
F. This is the stage when reproductive tissue development is occurring. Anthers, the pollen producing structures are easily damaged preventing or severely reducing pollen production. Barley is more susceptible to frost injury during the boot stage because it flowers while still in the boot. Winter wheat crops are at the greatest risk for injury from frost because they are in the boot to flowering stage. Evaluating these crops for damage must be done by dissecting flowers and looking at the anthers.