By Julie McConnell, UF/IFAS Extension
Five months ago, we experienced severe cold weather for three days which impacted landscapes across the panhandle. Since prolonged deep freezes are not common in our area we were unable to predict how plants would fare long term. As we progress into spring, it’s a good time to start assessing landscape plants and make decisions about what to keep and what to replace.
The plants we have received the most inquiries about at my office are citrus trees. Unfortunately, this category of beloved plants is difficult to protect and suffered dearly. The recommendation up to now has been to be patient and give them time to recover, but when should you stop waiting and what signs should you look for?
Obvious signs to look for are new leaves and stems, but the long-awaited appearance of green may not indicate recovery. Below are some guidelines you can use to interpret spring flushes.
Leaves and stems emerging in the canopy are a good sign if it expands fully and hardens off. This is a good sign of recovery because it indicates the trunk and woody branches are still alive. Ensure the tree has adequate water if rainfall is insufficient and if you fertilize do so sparingly.
New foliage in the canopy that dies before it fully expands indicates that the wood it was growing from was significantly injured. The failed regrowth is a secondary symptom of the initial freeze damage. Does that mean the tree will not recover? It’s a hopeful sign, but there are too many factors to give a definitive yes or no answer. If possible, give it more time to try to successfully replace damaged tissue. Limit pruning and fertilization, but provide water if rainfall is inadequate. If the tree makes another attempt at regrowth, be patient and don’t expect it to return to pre-freeze grandeur quickly.
Vigorous vertical growth from the base of the tree is also common and more complicated than it appears on the surface. Citrus trees are grafted and the new growth may be coming from the rootstock portion of the tree. Grafted trees have two parts – rootstock and scion; the scion is a plant with desirable fruit or other aesthetic features but has weak root systems. To compensate for subpar roots, they are grafted onto a hardier rootstock.
Rootstocks are selected for characteristics such as cold hardiness, disease resistance, and nematode tolerance. If the rootstock is allowed to sprout it ties up resources that the citrus scion needs to recover, so it is always recommended to remove those shoots. To watch a video demonstrating how to find the graft union on citrus see https://youtu.be/TaMF30sKRFE.
Secondary Pest: Ambrosia Beetle
When plants are damaged they produce volatile compounds that can be detected by insects that recognize that tree as an easy target for infestation. This year we have seen freeze-damaged citrus attacked by the wood-boring Ambrosia Beetle. Typically, this is not a common pest of citrus, but they are opportunistic insects that take advantage of severely stressed or dying trees. Inspect the lower 2-3 feet of trunks and look for small round holes that may have toothpick-shaped protrusions made of sawdust that shatter when touched. If you find signs of ambrosia beetle the tree will not survive and should be removed. There is no effective treatment for ambrosia beetle. More information on ambrosia beetle impacting freeze-damaged citrus is available at https://nwdistrict.ifas.ufl.edu/hort/2023/03/23/post-winter-storm-elliott-ambrosia-beetles-in-citrus.
If your citrus did not survive the freeze and you want to try again, here are some recommendations. Choose a space in your landscape that is sheltered from northerly winds. Select varieties that have the best cold hardiness such as kumquats and satsuma. If you decide to grow less cold hardy citrus such as lime or key lime consider growing in a pot that can be moved indoors in severe weather. For more information read Cold Hardy Citrus for North Florida.
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