To Prune or Not to Prune? That IS the Question.

  • 7 December 2018
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So WHEN is the best time to prune my cherry tree in the San Jose area?

As California residents get into the fall and winter, most gardeners start to think about pruning fruit trees. It is easier to see the branch structure of the tree as it is most visible when the leaves have fallen. The wintertime, is considered, the traditional time to prune deciduous trees. This is true for many shade and fruit trees. BUT, for some fruit trees pruning mainly during the summer growing season is a good practice for keeping the tree size in check. Also great for avoiding disease problems. Not to mention pruning during the winter months can prove to be downright harmful for some types of fruit trees.


Different Types of Diseases

Cherries, apricots and a few related species are particularly susceptible to fungal and bacterial canker diseases. Including Eutypa dieback, Botryosphaeria canker, and bacterial canker. Pathogens can be spread by tree wounds or rain — such as pruning wounds — during wet weather; subsequent infections spread through the wood for several years and may eventually kill the tree.

Trees infected with these diseases will see limbs, twigs or entire trees wilt and die suddenly in late spring or summer. All while the leaves are still attached. Bark may be darkly discolored and amber-colored gumming may ooze. If you cut into the branch, you will see infected areas in the interior of the wood discolored brown. Often times in wedge shapes.

Trees infected with the bacterial canker disease will show a cambial area on the limb that will turn red or speckled red and then brown. If you think you have one of these diseases on your tree, remove the infected branch by cutting at least one foot below any internal symptom of the disease, preferably during the dry season when the risk of spreading the infection is lowest.


Avoid Disease Problems

To avoid disease problems gardeners should not prune apricots and cherry trees during the typical rainy period from September through mid-April. Later rains can still lead to infections although tissue susceptibility to these diseases decrease with warmer weather. The first summer pruning can be done in late May or early June if growth is vigorous. At which time many strong upright shoots can be removed to allow sunlight to reach lower fruiting branches.

The main or final pruning should be done in August after the tree finishes fruiting. When executing heavy pruning, especially at that time of year, be careful not to remove more than one third of the overall canopy. Removing to much growth may lead to sunburned branches. Make sure to leave spurs and some other shoots to provide some shade to main tree limbs. Plus, you can whitewash west- and south-facing branches with a 50:50 mixture of interior, white latex paint and water to prevent sun burning.

If you have more questions about pruning, please go to our Contact Page and give us a call or submit a quick form. Happy Winter and safe pruning!

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