Winter Temperature Tolerance and Dormancy Requirements

• Apples are one of the hardiest fruit trees when it comes to winter survival. Being able to survive minus 60 degree is due to dormancy. During dormancy, buds are hardened and become less susceptible to frost damage. Apples have a chilling requirement to break dormancy and begin growth in the spring. Apples require between 1,200 and 1,500 hours of temperatures between 32 and 60 degrees with the best temperate about 43 degrees. For this reason, apples cannot grow where temperatures it does not get below these temperatures for the allotted number of hours.
  
  

Flower Bud Temperature Tolerance

• Apple flower buds have different stages of bud break and different temperature tolerances at each stage. There are nine bud-break stages that include: 1-Silver Tip, 2-Green Tip, 3-Half-Inch Green, 4-Tight Cluster, 5- First Pink, 6-Full Pink, 7-First Bloom, 8-Full Bloom, 9-Post Bloom. At stage 1, Silver Tip, the bud withstands temperatures down to 9 degrees, quickly raising to 24 degrees at stage 4-Tight Cluster. Exposure to 24 degrees for several hours at this stage will kill 50 percent of the blooms. At stage 5-First Pink, temperatures below 27 degrees kills 50 percent of the blooms.
  
  

Fall Harvest Temperature Tolerance

• Choosing an apple variety that ripens before a frost or freeze is important. Apples can be damaged severely by freezing temperatures that range from 27.3 degrees to 29.4 degrees with an average freezing injury temperature at 28.4 degrees. Apples subjected to this freezing temperature show damage to the inner flesh caused by the freezing of the cells. The freezing cells burst, causing cell death and appear as brown, soft spots in the flesh.
  
  

Storage Temperature Tolerance

• Not all apple varieties of apples store well so drying is an option.Hemera Technologies/Photos.com/Getty Images
  
  Apples can be stored for a long time if given the right temperature and relative humidity. Apples are best stored at 30 to 32 degrees with a relative humidity of 90 percent. Air circulation also plays an important role in delaying the natural ripening and aging process of the apple. Store apples in the refrigerator, root cellars, insulated out buildings or straw-lined pits. Whichever storage method you choose, do not expose the apples to temperature below 29 degrees, or freeze damage occurs.