Before
I explain why winter is the best time for pruning trees, I will discuss
how a tree should be pruned. There is a lot of incorrect pruning that
goes on by so called professionals, but I will save that discussion
for another time, when I discuss how to prune trees in more depth.
Cutting
trees causes a certain amount of damage to them and possible exposure
to diseases, so you should always have a good reason for pruning a
tree. You should make only the cuts necessary and make cuts correctly.
There are two considerations when pruning, pruning for the tree's
health and pruning to help the tree develop a strong structure. (There
are other reasons for pruning which I will not discuss now, such as
space issues- keeping trees out of wires and off of buildings; artistic
pruning such as Bonsai pruning and pruning to maintain a view.) Pruning
for health and structure should be the most important considerations
for any pruning.
Branches
that are unhealthy, dead or dying, or growing incorrectly should be
eliminated from the tree on a regular basis to help the tree maintain
healthy foliage. The structure of the tree should be examined on a
regular basis and if necessary some branches should be reduced or
eliminated to help the tree develop a strong structure that will hold
up to Colorado’s weather. Branches should not be eliminated
without there being a good reason for their elimination, the tree
needs as much healthy foliage as possible.
There are biological reasons for pruning in the winter when the tree
is dormant (less active). They have to do with the loss of foliage
which produces sugar for the tree to live on and the storage of this
sugar for tree use. Basically, there is less loss of important sugars
during winter pruning. There are also considerations of disrupting
hormone distributions in the tree at other times of the year that
are not as strong in the winter. It requires energy for a tree to
begin the process of closing off a wound to stop decay, there is less
competition for the energy resources in the winter.
There are health reasons for pruning in the winter. Bacterial and
Fungal diseases are much less likely to infect a fresh cut on a tree
in the winter. There is little or no insect activity in the winter,
so fresh cuts don’t attract damaging insects like they do at
other times of the year.
There
are practical reasons for pruning in the winter. Deciduous trees loose
their leaves during the winter and it is much easier to see the tree’s
structure and inspect for flaws and weakly growing branches when leaves
are gone. It is easier to get an overall view of the tree’s
structure and growth patterns and therefore determine where to make
cuts that will correct weak growth patterns and balance the tree.
A
common question is: How can you tell what is dead and what is living
when you prune during the winter? Most trees have very obvious buds
on living branches that will turn into leaves in the late spring.
Branches that were dead during the summer do not have buds during
the winter. Also, on dead branches the bark will look dried and crinkly;
it usually changes color which makes it easy to determine what is
dead and what is living. However, a branch that was alive during the
summer but dies during the winter may not be easily recognized until
the following summer. Any professional arborist should be able to
tell the difference between dead and alive branches during the winter,
and you can too if you take some time to observe trees.
