When you should prune depends on what kind of tree you have. Most do well with winter pruning, but there are a few exceptions.
Winter pruning season is approximately December to mid March. Once the new growth begins to emerge in late March/April (new flowers and leaves) the plants are using lots of energy. At that point, it isn’t the best time of year to do heavy pruning.
A few things to keep in mind when you prune trees:
- You can prune dead wood off a tree at any time of the year. Deadwood is not metabolically active so removing it causes no stress to your tree.
- Be sure you have a good reason to prune your tree, otherwise you may be causing damage without getting any benefit. Don’t just prune because that’s what the neighbor does!
- Be sure you have the time, energy and expertise to prune.
- Know what type of tree you have and if winter pruning is appropriate.
Deciduous trees that drop their leaves in the winter—like Maples, Crape Myrtles, or Chinese Pistache–are dormant at this time, so pruning now works with the tree’s own internal timing. When the tree starts growing again in the spring, it’s energy will not be wasted growing in directions you do not want it to go. And because the leaves are off the trees, it is easy to see the structure of the tree and what needs to be corrected. Be aware that the flower buds are already forming on most deciduous trees, (those are the rounder ones; the leaf buds are usually longer and less round) and you may not want to remove an excessive amount of the flower buds if you want the flowers or fruit. The University of Florida has lots of information about pruning shade trees.
Fruit trees that drop their leaves in the winter need to be pruned according to the pattern that is suited to their growth and fruiting type. Pears and apples are usually pruned with a central trunk and side branches. It’s best to do the major pruning of these trees in the winter. “Stone fruits” like peaches/nectarines, plums, cherries and apricots are generally best pruned in a vase-like shape (open center) with no central leader. Since stone fruits grow fast and large, pruning them in the summer and winter helps keep their size in check, but DO NOT PRUNE APRICOTS in the winter. We have a fungal disease that spreads in the rainy season and can kill winter-pruned apricots. Apricots should be pruned in the summer right after harvest, that way they can avoid the often fatal Eutypa fungus. When pruning fruit trees, keep in mind that most are “semi-dwarf” in size and can grow to be 15’ tall. It is much easier to harvest fruit off a tree you don’t need a ladder for. Consider pruning to keep the tree short enough so all the fruit can be easily picked without a ladder. Lots of information on all types of home orchard trees is available at the Backyard Orchard website from University of California at Davis.
Citrus trees can be pruned in the winter if you are careful of the flowers and flower buds for next year’s fruit. The flower buds often start opening when the fruit is ripening or a little later. Removing too many of the flower buds means you will be reducing the fruit for next year. Depending on how much of the fruit you like to eat, this could actually be helpful. Citrus need little pruning to be fruitful, and may be shaped to suit your landscape. Keep in mind that even semi-dwarf citrus can be taller than you can easily reach from the ground, so you may want to focus on controlling height. If your citrus has been damaged by frosts, wait until the new growth comes out in the spring and remove damaged branches that have not sprouted new growth. The University of Arizona has a good resource for pruning citrus.
Evergreen trees with broad leaves–like Magnolia, Camphor, or African Sumac–can also be pruned in the winter. Because they have a full canopy all year, it can be more challenging to see their form. Move around
the tree and look from several directions to get an idea of which branches might need to be pruned.
Evergreen conifer trees with needles or scales–like Coast Redwoods, Pines or Cypress–usually need little pruning and are not generally tolerant of heavy pruning. Don’t cut off all of the green growth on branches as the branch will usually be unable to sprout new growth, leaving an ugly dead branch. Winter is a good time to prune most conifers. Get more information on pruning conifers.
Palms need pruning to remove the thatch of old leaves that hang down the trunk. These old leaves can be 3’ long and often have sharp teeth on the stem. If they break off and fly around in the wind they can cause damage. Also, the thatch is a favorite place for vermin to live, so having it pruned is desirable. Some palms are not frost hardy and may be damaged if the temperature falls much below 32 degrees. Queen Palms are often planted in Roseville, but are not fully hardy here. If your palm shows damage after a freeze, wait until spring to remove any dead fronds, as they provide some protection for the new fronds that will emerge in the spring. Pruning palms is a good job for an experienced arborist. The International Society of Arborists has tools to find an arborist or check credentials.