Taking Care of Trees After the Five-Night Freeze

Josh McGillCold Hardy, freeze

“To some extent, every citrus variety has suffered from cold damage” due to the five-night freeze event that occurred in the cold-hardy citrus region Dec. 24–28. That report comes from Jake Price, Lowndes County Extension coordinator for University of Georgia Extension.

five-night freeze
Figure 1. Owari fared the best after the freeze.

“The site of our citrus research plots in Valdosta reached a low of 16 degrees, which is the lowest I have recorded since the trials were installed,” said Price. “When temperatures are that low for that long, there is not much that can be done to protect citrus, and damage is to be expected.”  

Price recently answered the following questions to give guidance to Georgia Citrus Association members on what to do after the five-night freeze.

five-night freeze
Figure 2. Glen navel trees looked the worst after the freeze.

What is happening with cold-damaged citrus trees? 
It takes time to know the extent of damage that has occurred to citrus trees. Obvious early symptoms of damage are leaf curl and tanned foliage. After a few days, many trees begin to shed leaves. Some green foliage that looks okay may also drop. This is actually a good sign because trees and or limbs that are killed by a freeze do not drop leaves. Foliage that turns tan and sticks to the tree indicates the limb or tree has died. It is common to see younger late-season growth die back from freezes while order growth on the same tree appears okay.

What do I do now to my damaged trees? 
Do not prune citrus trees now. We do not yet know the extent of damage to limbs, branches and the trunks of trees. By May or June, limb damage will be obvious. Wait until then to prune these dead limbs by pruning into the green wood below the dead wood. Any fruit left on trees was frozen and is no longer good. In general, frozen fruit is only good to use as juice, but fruit should be juiced within a couple of days after freezing.

five-night freeze
Figure 3. Sugar Belle appeared worse than expected post-freeze.

How can I protect my trees for the rest of the winter? 
Winter has just begun, so it is possible there will be more damaging freezes. With trees already damaged and with much less foliage, they will be more susceptible to freezes, so things can get worse. Growers with freeze protection should use this if there are more predicted freezes. At this point, it is better to be safe than sorry. So, if there is any question, go ahead and freeze protect. The goal of freeze protection is to save as much of the trunk above the graft union as possible at the expense of the rest of the tree during these extreme events. If the graft union is saved, the tree will regenerate, but a year or two of production will be lost.

What varieties were the most damaged? 
From my observations at this point, it appears the satsumas have handled the freeze the best. This is expected as they are known for cold hardiness, and that is why many have been planted in Georgia. Lemons, grapefruit and limes appeared to have the most damage. Everything else is somewhere in between. At the research plot in Valdosta, the only trees I freeze protected were the Tangos because our water is limited, and they are the youngest trees. The Sugar Belles, Owari satsumas and Glen navels were on their own.

The Owaris are currently dropping foliage and appear to have the least damage at this point (Figure 1). The five Glen navel trees look the worst (Figure 2). The Sugar Belles look worse than I would have anticipated because they are large trees and have endured cold weather well to this point (Figure 3). The Tangos are damaged, but I am hoping they will retain some foliage and produce a crop again next year (Figure 4). They were freeze protected for five nights in a row! They were the youngest trees planted in 2020. The tops are all new growth, and much of that appears dead. They were going to be pruned anyway. 

five-night freeze
Figure 4. Tango trees suffered damage despite freeze protection with microsprinklers.

Were there any silver linings to the freeze? 
This freeze event will let us know the cold tolerance of many citrus varieties. I have conducted Brix and acid tests on 30 varieties, just around Lowndes County, so there are a lot of varieties planted. We will find out which varieties we need to plant and the ones we need to avoid. Also, with the threat of huanglongbing (HLB) looming all around, these low temperatures will no doubt harm any Asian citrus psyllid (ACP) population that may be trying to establish in Georgia. ACP vectors HLB.

Refer to this University of Florida Institute of Food and Agricultural Sciences publication for more information on freeze damage and recovery.

Source: Georgia Citrus Association

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