FALL IS HERE… The leaves of the deciduous trees are beginning their color changes as they prepare to rest for winter. Fall months are the busiest time for the tree trimming/pruning industry. Two of the bigger reasons for this is that people don’t like the leaf litter that quickly accumulates and Santa Ana winds tend to begin in late September or October which can lead to tree limb damage. Both are good reasons for trimming/pruning but you might be surprised that most people believe it’s the best or only time to trim/prune trees. This idea has been passed down through the years and has become the unofficial truth. We are not suggesting that the idea doesn’t have any merit, but you might be interested to know some other factors that might give new insight or truths when it comes to trimming/pruning.
For example, trimming/pruning in the spring after bud break can slow a trees growth for the season by reducing the amounts of growth hormones that are located in the shoot tips and root tips. So when the amount of shoot tips are reduced so are growth hormones. It is also easier to see the dead wood as well for easy removal. In truth, proper trimming/pruning can essentially be done any time of year. The exceptions that could apply to that statement might be Pine trees. They are best trimmed/pruned in the winter months when the pest population is low or dormant and their sap is much thicker to reduce loss after trimming/pruning. Another exception might be with fruit bearing trees. They are best to trim/prune after fruit harvest and before flower production if maximum fruit production is the goal. With Stone fruit trees, fruit is produced on last years growth so be careful what and how much you remove. Summer is never a good time for heavy trimming/pruning of trees as the sun can damage tree bark. If it means preventing tree or limb failure it might be worth the risk. Some evergreen-leafy trees have very thin bark such as Olive and Citrus which succumb to sun scald very easily in the warmer months.
So it is reasonable to say that proper trimming/pruning can be done most anytime of year. The Industry Standard for foliage removal when trimming/pruning is 15-25%. Removing more than the maximum 25% will likely cause the tree to grow back faster than wanted. Leaves are energy producers or think of them as solar panels. It takes a certain amount of leaves to support the tree from the roots up. Exceeding the minimum amount it needs may cause the tree some stress, which usually triggers a hyper-re-growth and can reduce the stored energy in reserves. Repeated over- trimming/pruning could lead to decline or death of the tree. For further details on this topic and many other wonderful tree related information, visit the ISA International Society of Arboriculture at www.isa-arbor.com.