Influence of Winter Weather on Blueberry Production in Florida

Weather plays a prominent role in yield and productivity of blueberry farms in Florida. The consecutive winters of 2010–11 and 2011–12 were very different with regards to chill accumulation and incidence of late winter freezes. During the 2010–11 winter, chill accumulation was above average and no severe freezes occurred after bloom initiation. Conversely, during the 2011–12 winter, chill accumulation was below average, especially in south Florida, and two back-to-back freezes occurred in mid-February after initiation of bloom and spring growth. Moreover, in 2011–12 most of the chilling occurred relatively late in the winter. By 28 Dec. only 16 h of chilling was recorded in Polk County, FL. Hydrogen cyanamide, a growth regulator used to assist in satisfying chill requirements, was more effective in northcentral Florida than in south Florida. Hydrogen cyanamide is typically most effective when plants are fully dormant and significant natural chilling has occurred before its application, conditions which were more likely to have occurred in north-central Florida than in central or south Florida during the 2011–12 winter. The combined effects of below average chill accumulation and severe freezes reduced statewide production in 2012 compared to 2011. In north-central Florida freeze damage was highly variable depending on cultivar, location, and the freeze protection system employed. Generally, early-flowering cultivars, such as ‘Snowchaser’, ‘Meadowlark’, and ‘Springhigh’, sustained greater damage than later-flowering cultivars, such as ‘Emerald’ and ‘Jewel’. In south Florida, most cultivars showed symptoms of insufficient chilling; bloom was delayed and protracted, and yields were below average. Generally, the best production occurred south of Ocala and north of I-4 where modest amounts of chill were recorded and freezes were not severe.