The early spring months of late February to about mid April causes a lot nervousness for those of us that farm tree and vine crops. This tension is the result of the possibility of frost, especially if one is in an area more susceptible to frost (usually low lying and wind sheltered). A couple of hours of these frigid temperatures can have immeasurable effects. Throughout the spring as tree develop their fruit into nutlets and grapes develop shoots, this soft, tender tissue is extremely sensitive to freezing temperatures. A few hours at 32 or lower can either completely “burn” the developing crop or significantly reduce it. The weather patterns during this time period are extremely erratic, one can have a 70 degree day and the next day it could be in the 50s. Most frost events occur after a storm system passes through then skies clear and winds die during the evening. Dry springs like we are experiencing this year always have storms come over with no or little precipitation but cold temps.
The question then becomes what can a person do to mitigate or at least put yourself in the best situation to have little or no damage. Over the years numerous things have been learned: 1. Hard soil with little or no vegetation is the warmest. 2. Evaporating water has a warming effect. Growers use these bits of information to affect the temperature in the orchard/vineyard, a few degrees difference in temperature can be extremely significant in most cases. A lot of preparation is still in order, one of the main things is first having enough water and the ability to get the water across the field during the cold event. Numerous physical limitations can exist and it may not be ideal but the attempts are usually worth it. If there is a little cloud cover and light winds the extra degree of warmth will be beneficial. Many times it becomes a matter of luck. Most of us have seen a field where part of field was mowed and the grass was left very low suffer no frost damage whereas the other part of the field with a 6” grass cover have noticeable frost damage. The literature says the difference in temp is only a few degrees but the physical damage seen is huge.
As the days get longer in April and the warm days predominate the threat slowly diminishes. That said, some of old farmers say that their grandparents remember a really bad frost at around the end of May that wiped out a lot of crops in the late 1930’s. I guess the threat of frost is always out there like any other natural weather phenomena. Hope everyone survives this frost season OK.