There are many benefits to pruning your trees. Keep in mind that they are living dynamic entities, constantly growing and changing, just like you and me! So, by removing damaged and diseased branches, your saplings are encouraged to work harder, grow better, add foliage faster, produce stronger flowers and fruits, refine its shape and even improve your lovely view. These are just some advantages.
Learning how trees grow will help you gain confidence and provide more bang for your pruning buck. A tree doesn’t stop growing because you pruned it. Over time it will replace foliage that was removed and probably add more to it. Sometimes the growth happens within 12 months, sometimes it will take years.
The truth is, any time of the year can be the right time for pruning depending on the species and your motivation. Consider a Monterey pine that has a fractured branch, hanging over a children’s play area in the middle of summer. As you can guess, pruning it in July is the absolute right time. The need for safety overrides the best time to prune a Monterey pine, which is actually in winter to avoid insect infestation.
Trees expend a lot of energy shedding their leaves in the fall in preparation for the dormant season, and also expend a lot of energy producing new foliage in the spring. From an arboricultural perspective, the best time of year to trim is the middle of winter or summer for the benefit of the tree’s overall health. However, in California’s mild climate, it can be tricky with some plant species which, when pruned at certain times, are susceptible to certain insects and diseases.
Here is a short list of native California trees the recommended time to prune:
Alders: Prune in winter to avoid borers
Apricots: Prune in July/August, as they are susceptible to a disease (Eutypa dieback) that is spread during wet weather
Birches: Prune in September-March to avoid bronze birch borers
Citrus: Prune in April (after all danger of frost is gone) through August. Pruning tends to stimulate growth, and tender foliage on citrus can be damaged by frost. Pruning too late in the year may increase the chances of frost damage.
Conifers (cedars, spruce, fir, etc): Can be pruned at any time of the year, but these trees have a tendency to bleed from the pruning cuts, which may be worse in the warm summer months than in winter. If the tree hangs over cars, winter pruning may be better to help lessen sap drop.
Cypresses: Prune during dry summer months, as they are susceptible to a vascular disease (cypress canker) that is spread through water
Fruit trees: Prune in December & January if fruit production is a top priority. If the tree is valued as ornamental first and the fruit is a secondary benefit, then you can prune the tree at any time of the year. However, for Apples & pears with fire blight, prune in summer or winter when the bacteria is not actively spreading (avoid spring or rainy season).
Monterey Pines: Prune in November through February, when the bark beetles are dormant
Mulberries: If the tree is being pollarded every year, prune in December & January after the leaves drop. Any regular non-pollard pruning can be done year round.
Raywood ash: Prune during dry summer months, as they are susceptible to a disease (Ash dieback, Botrysphaeria) that is spread through water.