Summer Pruning
By Jutta Thoerner UCCE Master Gardener
I moved and have inherited several fruit trees that are huge. Can I prune them now? Edwin, Atascadero
Yes, summer pruning to reduce the overall size of a tree can be done now. Studies have shown that next year's shoot growth, flowering, or fruit is not affected by summer pruning, even if up to 30 % of foliage is removed. Before you start summer or winter pruning, sharpen your tools and have a container with a 25% diluted bleach solution ready. Disinfect tools between cuts and between trees to prevent the spread of cankers and bacterial diseases.
Since your trees have been neglected, concentrate this summer on reducing the height of the tree and getting light into the center of the tree. This is done with thinning cuts to the center of the tree and by removing up to 30% of branches and foliage from the top and sides. If your summer pruning leaves some branches overexposed to the sun, beware of sunburn. Mix a 1:1 solution of white interior latex paint and water to seal the exposed branches and protect them from sunburn and invading beetle borers. Cherry and apricot trees are only pruned in the summer because they are prone to Eutypa dieback, a branch killing canker disease that spreads with moisture. Pruning in the summer will ensure 6 plus weeks of dry weather after the pruning cut.
If you did not thin your fruit earlier in the season, shorten extra-long fruiting branches to prevent a heavy fruit load and possible breakage, a method often done with peaches. If your goal is to reduce the height of your fruit trees to better fit your needs, several seasons of winter and summer pruning on large trees will be necessary. Once the trees are that perfect “you” size, there is nothing more satisfying then reaching that nectarine from a top branch; no ladder necessary!
To learn more about summer pruning and to see a live demonstration on different fruit trees, visit our Advice to Grow By workshop on June 20th from 10 am -12 pm in the Garden of the Seven Sisters in San Luis Obispo. The garden's docent hour will immediately follow from noon to 1:00 pm.