Preparing for the Freeze

Your Winter Crop Survival Checklist 

by JEFF WILLIAMSON, Horticultural Sciences Department, UF

& DOUG PHILLIPS, UF/IFAS Blueberry Extension

As the new year gets underway, many blueberry growers are already thinking about the upcoming bloom period and the possibility of damaging freezes. The checklist provided below is a good place to begin reviewing preparedness for protecting against damaging freezes that often occur before, during, and shortly after bloom. Being well-prepared will reduce stress and increase the likelihood of a positive outcome. 

During late winter and early spring, growers will probably need to make important decisions concerning if, or when, to protect against a potentially damaging freeze(s). These can be among the most complicated and critical decisions that regularly face blueberry growers almost every year. Many variables can affect whether or not, and when, to freeze protect. These include, but are not limited to, forecast information such as predicted minimum temperature, dew point temperature, wind speed, and length of freeze. Crop development stage (hardiness) and freeze protection system capabilities are also important considerations. 

Here are several resources that growers may find helpful to review before the upcoming blueberry bloom season.  

Winter Freeze Checklist 

Virtually all blueberry fields in Florida are subject to late winter or early spring freezes that can cause serious reductions in yield. Below is a list of activities for freeze preparation. The list was originally published by Mike Mainland in the North Carolina Blueberry News, Vol. 7, No. 1and it has been modified by IFAS faculty and FBGA board members over the years. 

  1. Flush all overhead sprinklers to clear debris – remove heads and flush.

  2. Test and service the pumping units, replace filters and have spare filters available.

  3. Treat diesel tanks for water and algae.

  4. Check lines and sprinklers in the field for leaks and clogged nozzles. 

  5. Check water pressure on ends of distant lines.

  6. Make sure drainage in and around fields is adequate. Make sure roadways around and through the fields will withstand traffic at night during irrigation. 

  7. Remove or relocate any equipment that may impede or pose a danger to vehicular traffic.

  8. Have a (remote-controlled, magnetic roof-mounted) high-intensity spotlight ready to plug into the truck to check sprinklers. 

  9. Put shielded minimum thermometers in cold, average, and warm areas of fields – at the average height of the middle of the bushes,

  10. Consider purchasing weather stations that communicate real-time weather conditions to computers and smartphones. 

  11. Hang some ribbons on trees or poles around fields to detect slight breezes.

  12. Identify a good source of agricultural weather information and watch it closely. Consider subscribing to a weather service that issues freeze warnings. 

  13. Consider purchasing a monitor that calls you when the temperature gets low. 

  14. Consider purchasing a handheld wind meter or anemometer to measure wind speed. 

  15. Consider purchasing a sling psychrometer to measure wet bulb and dry bulb temperatures, relative humidity, and dew point.  

  16. Have rain suits and boots available for everyone responsible for checking the irrigation system.

  17. Have wires available to unclog nozzles.

  18. Have tools and replacement parts that are necessary to exchange nozzles and/or sprinklers. 

  19. Be certain you know the “safe cutoff temperature” before you shut down your overhead freeze protection irrigation. This temperature can be as high as 40 degrees F if the dew point is low and wind is high. 

  20. Fill all vehicles with fuel before the freeze event.

  21. Have help available or on call if needed for emergencies.

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