by Steve Turner
When Is The Best Time to
PRUNE TREES
& SHRUBS?
I am often asked when the best time is what should
be pruned. The ideal time is when the tree is dor-
mant, which is late fall to early spring. Since the tree
is not active, the removal of limbs will be less stress-
ful to the plant. It is also easier to see the structure of
the tree without its leaves to better fi nd problem areas
like rubbing branches, weak crotches, cracked or bro-
ken limbs and competing leader branches. The tree
will have more time to seal the wounds before the
growing season starts and there will be less sap run-
ning from the wounds. Also, insect and disease organ-
isms are not active at this time, so it reduces the risk
of infection or pest infestation, which is why birches
and American elms should only be pruned in the win-
ter. The worst time to prune trees is late spring and
early summer when their leaves are expanding and
the tree is putting its energy toward growth.
A common myth is that large, mature trees can toler-
ate more pruning than small trees. In fact, the op-
posite is true. Only the outside inch or two of a tree
is alive; the rest is made up of dead cells whose main
function is to support the tree. That’s why a tree can
be hollow but still be perfectly healthy. If you com-
pare the percentage of live cells to dead cells between
a small tree and mature tree, the difference is huge.
A young tree might be made up of 90 to 100 percent
live cells, while an old, mature tree might only have
10 percent or less. As you can imagine, the younger
tree has a better chance to adjust to change.
A good rule for mature trees is that less is better. Try
to avoid removing large limbs over 6 inches in diam-
eter because it will be diffi cult for the tree to close the
wound before decay sets in. Other options are cabling
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or thinning these large limbs as opposed to removing
them. Good maintenance items for mature trees are
removing deadwood and hazard limbs and thinning
for weight reduction when necessary.
Young trees up to 8 to 12 inches in diameter need
to be pruned properly for structure while they are
still young to avoid the need to remove large limbs
in the future. When pruning trees, keep in mind that
the leaves produce the energy for the plant and that
removing too much leaf surface from a tree or limb
will starve the plant, causing die back or heavy sucker
growth from that part of the tree.
“Topping” trees destroys them. They will never grow
back to their natural shape and every branch that
grows out of that wound area will be an accident
waiting to happen. As the new limbs grow bigger and
the rot in the wound increases, the branch will even-
tually break. A topped tree soon becomes a mainte-
nance headache, with constant storm damage due to
the weak branch attachment. If a tree is too large for
its location, consider having it removed and replanted
with a smaller species rather than topping it.
It is important to know what a tree’s natural shape
will be when it matures before you prune it. For ex-
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July 2019