I’m commonly asked what time of year is best to prune pecan and other deciduous trees. The answer is right now, this very minute. Deciduous trees are best pruned when they have lost their leaves in the winter. Pruning at this time decreases the likelihood of the wounds getting infected with disease, and it’s easier to see the limbs.
While this is the ideal time to prune, it doesn’t mean you can cut as much as you want from a tree. Mature shade trees should not be pruned more than 25% of their total canopy. Cutting off more than this takes away from the tree’s energy stores and may stress the tree, which can lead to disease and potential death.
You need to prioritize what gets removed. For mature shade trees, focus mainly on removing damaged and diseased limbs first. Then choose limbs that rub together. Then you may thin the canopy, keeping in mind that you cannot remove more than 25%, and what you have removed already counts.
Topping trees should be avoided unless it’s a last ditch effort. In February 2021, we had that ice storm and the cold weather damaged most of the Arizona ash trees in town. Since the branches up in the canopy were dead anyway, and the other option was to remove the entire tree, I recommended that these trees be topped. Some of these trees have regrown a canopy once more, some of them have died and some have a couple of limbs extending from a tall stump. Results were variable, so this isn’t recommended for perfectly good trees.
One a nnoy ing habit of local tree trim- mers is “lion tailing,” remov ing all the limbs so that there is only a tiny tuff of canopy up top. While I understand that this allows more sunlight to reach the grass and I haven’t seen a tree killed by it yet, it’s not good long term for the tree.
Most trees I’ve seen that have been lion tailed respond by growing many new sprouts on the trunk where the limbs were removed. Lion tailing also puts more of the leaves and branchlets at the end of the limb, making it heavier at the end, which makes it more likely to break in heavy winds and during ice storms. Additionally, the loss of interior canopy means the tree cannot use photosynthesis as well on hot days, because the cooler interior leaves are gone. When done well, this may look aesthetically appealing, but it’s not without some risks. This is not recommended for stressed trees.
Young shade trees are pruned somewhat differently because they are being trained for their final form. Make sure the tree is maintaining a single leader, or a single limb reaching upward above all other branches. Remove branches that form a sharp V angle to the trunk. Also remove rubbing limbs growing inward, and root suckers from the base.
When pruning these trees, unless the tree is an oak, you do not need to use pruning spray. This actually slows healing when compared to leaving the wound unsprayed.
Live oaks can be pruned this time of year too, even though they have foliage still. To decrease chances of oak wilt, live oaks should be pruned on the coldest part of winter when the beetles are not active for several days, or the warmest part of summer when the oak wilt spores fry in the heat. The beetles should be less active right now, but when we have brief warmer days, they may stir. Because oak wilt is so common and deadly, it’s best to assume it’s a threat, and spray the pruning wounds after every cut. Make sure to also clean tools between healthy live oaks and live oaks with oak wilt, unless using a hot chainsaw.
For information call the AgriLife extension office at 830-997-3452 or email Elizabeth.mcmahon@ag.tamu.edu.
