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Can row covers be used to protect my grapes during a spring freeze?


Spunbon polyester row covers, such as Agribon™ or Reemay®, act as blankets which slows the rate of heat loss from the soil.  Row covers protect plants by trapping heat released from the soil and are available in several weights and dimensions.  The heavier the row cover, the more protection it provides but the less light is transmitted.  While very common in vegetable production, they are very cumbersome to place over high-density orchards and vineyards due to wind.  A 0.5 oz/yd2 cover will provide 2°F to 4°F of protection outside.  They must be closely monitored so that temperatures do not get too warm during the day.  If it is a sunny day, expect to have to remove the cover.

This has been tried over trellis systems using bird netting machines.  The wind prevents you from being able to actually put the row covers over the row.  This is not an effective (practical) method of preventing late spring freeze damage to plants.

Is there a magic potion I can spray on my grapes to give them super freeze prevention strength?


The simple answer is no, there is not something that can be sprayed on plants to give them protection from late spring freezes.  However, there are all sorts of trials and testimonials using foliar potassium (Nutri-K, Agro-K), carbohydrates, and sugars sprayed onto plants a few days prior to cold temperatures setting in to help plants survive.  Each product is basically acting like antifreeze (prevent nucleation) in the cell to prevent internal freezing and cell bursting.  It is very difficult to get good data on farms on in research field trials to verify when/how/if these products actually work.  Conditions vary so much from site to site and year to year that we don't have replicated data to stand by (remember that ISU is reserach based guidance).  At this time, I cannot say there is solid evidence of any product being affective consistently and in replicated in trials.  A lot of factors go into it including timing, product, and rate (and probably a bunch of other things).