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Summer Pruning
“If it doesn’t hurt, do it!”
This is the motto that those who practice preventive pruning
during the summer months use to justify removing living limbs. Some
softhearted people cannot imagine brutalizing actively growing plant
life. These same people do not hesitate to even use a chain-saw on their
plants during the “dormant” season. Such dormant-season-only
pruners actually encourage the major surgical cuts that will be necessary,
because they’re unwilling to engage in minor preventive surgery
during the tree’s active growth cycle. Most of us have heard such
sayings as “nip it in the bud” or a “stitch in time
saves nine”. This type of philosophy definitely applies to summer
pruning. You have the choice—do a little now, or a lot later!
Any pruning should have a purpose. Reasons to prune include
dead wood removal, removal of damaged or rubbing branches, size and
shape control, and fruit enhancements.
Fruit enhancement caused by winter pruning occurs due
to the removal of excess fruit buds. This prevents overbearing and,
consequently, poorly sized fruit the following spring. With summer pruning,
the opposite is accomplished. Fruit bud production is enhanced. If not
summer-pruned, fruiting wood down in the inside of peach trees can become
shaded. Current- season shoot growth that is shaded will be short in
length and weak.
In a single season, shade can reduce vigor and even cause death of fruiting
wood. As a result, the area of productive, fruiting wood of the tree
simply moves higher up and the center remains fruitless.
The appropriate amount of pruning depends on whether
trees were pruned the previous winter, the extent of the pruning and
tree vigor. The main objective of any summer pruning is to increase
light penetration and maintain the vigor of fruiting wood in the major
fruiting zone of the tree. In general, this is accomplished by:
1) Reducing the height of trees to permit light penetration
within the major fruiting zone.
2) Thinning cuts within the tree to permit light penetration
within the major freeze zone.
3) Selective removal of vigorous suckers that develop
on the inside of the tree.
The actual amount of pruning must be determined on a tree-to-tree
basis. In general, very vigorous trees would benefit from at least 2
to 3 thinning cuts in each quarter of the tree (1- to 2- inch limbs),
and removal of most vigorous watersprouts from the center of the tree,
particularly arising from previous pruning cuts within the major fruiting
zone. These few but relatively big thinning cuts will go a long way
towards increasing light penetration without stimulating excessive re-growth.
As for timing, there is little data to tell us when to
summer prune so that fruit wood for the next year is ensured. However,
we do know that peach flowers begin initiating in early July. Severe
summer pruning late in the season (July through August) results in growth
that forms a low percentage of flower buds. This is not an important
factor when considering non-fruiting trees. In fact for non-fruiting
trees, the month of August is a good time to prune deciduous trees.
By this time, most of the terminal and diameter increase (plant growth)
has occurred; and, physiologically, it has been shown that there is
good wound response at this time. For years, nurserymen removed suckers
and unwanted branches during this month. They took advantage of the
foliage being on the plant as long as practical, thus adding dimension
to the tree trunk, but removing the unwanted growth at a time when the
plants calloused over most rapidly.
Summer pruning can be a tremendous benefit when winter-pruning
time rolls around the following February. On mature trees, all excessively
vigorous shoots should be removed during summer pruning. Suckers and
watersprouts will grow extremely fast up through the center of the tree.
A mature peach tree should not develop over 12 to 18 inches of terminal
growth each year. If you have excessive peach tree growth over this
length, cut back on next year’s fertilizer and do not prune as
hard during the dormant season.
On young peach trees, small shoots that grow straight
down from the main scaffold or sub-scaffolds of trees that are 2- to
4-year old should be removed during summer pruning. One out of every
5 shoots on the scaffold or sub-scaffold limbs of a young tree will
grow directly into the center of the tree. These shoots should be removed
during summer pruning. Vigorous terminal shoots making excessive upright
growth should be headed back by removing the vigorous central shoots.
Small side shoots will then develop and produce fruit buds for next
year’s crop. Never over-prune the growth in the center of the
tree. Enough small shoots should be left to provide shade for the scaffolds
and sub-scaffolds. Over-exposure of scaffolds to sun will result in
“sunscald”, i.e., death of the upper side of the exposed
scaffold.
Many of you have planted peach trees just last spring
and are wondering what you should be doing. You definitely need to summer
prune!
Within a few weeks after growth begins in the spring,
begin the selection of 3 vigorous shoots arising from the top 6 inches
on the main stem. They should be evenly spaced 4 to 6 inches apart along
the trunk, and one of these should be directed into the prevailing southeast
wind. Cut back all other shoots to prevent competition within these
3 scaffold limbs.
The peach trees should make maximum growth during the
first and second years. It is extremely important to direct this growth
into the permanent scaffold system. In order to properly train these
vigorously growing trees, summer pruning is necessary.
At planting time, 3- to 4-foot peach tree nursery stock
is pruned to a single trunk and headed back to a height of 24 inches
tall. All branches are removed and the lower 18 inches of trunk is wrapped
with aluminum foil, felt paper or any other opaque materials. This wrap
inhibits suckers along the trunk.
During the first growing season, the peach tree scaffold
limbs should be allowed to grow as much as possible. On vigorously growing
trees, the aluminum foil should be removed in July to prevent the bark
from growing into the wrap. All new shoots should be cut back periodically
to 4-inch stubs. This “trashy-trunk” helps reduce sandblast
and sunscald. If the major scaffold limbs grow at least 36 inches during
the first season, head them back to a length of 32 inches to encourage
the sub-scaffold system.
During the first winter, cut off all branches arising from the main
stem except the 3 scaffold branches. These limbs should be 32 inches
long with sub-scaffolds chosen to develop the horizontal spread of the
tree. Watersprouts and suckers arising on the lower parts of these main
branches should be removed.
Two sub-scaffolds should be selected on each major branch
as soon as possible. These begin approximately 32 inches away from the
trunk and develop the horizontal fruit-bearing surface of the tree.
Horizontal growth is encouraged during the second growing season. All
upright sprouts are removed in the center of the tree to allow horizontal
fruit wood to develop for next season. Periodic summer pruning will
be needed throughout the season.
Summer pruning has been practiced for many years in Europe
to contain trees in hedges and espaliers and to obtain the uniform ripening
of fruit. In this country, summer pruning is rather new and is gradually
becoming an annual practice to maintain smaller tree size and improve
fruit size and color.
Removing leaves by cutting off some current and 1-year-old
shoots reduces the growth-manufacturing power of the tree and, therefore,
leads to temporary slow-down in tree growth. At the same time, more
light penetrates the tree center causing inside leaves to become more
efficient, which leads to improved fruit color and quality through the
entire tree. By pruning in June, you can see which part (fruit area)
of the tree is or is not receiving adequate light. So, by making 1 or
2 minor cuts, you can seed how light reaches the inside. This is most
noticeable when pruning is done on a sunny day.
Most people cringe at the thought of cutting on their
precious fruit tree “while it’s living”. But just
remember—do it now or do it later! Cuts now will be minor surgery
compared to the major surgery that will be necessary later to remove
larger branches which wouldn’t exist if you had done what you
have in the summer months.
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