The reasons for pruning can be grouped under the four
following categories: training the plant; maintaining plant
health; improving the quality of flowers, fruit, foliage, or
stems; and restricting growth.
Training the Plant
The first pruning of young trees and shrubs consists of removing
broken, crossing, and pest-infested branches.
With trees, the rule of pruning away 1/3 of the
top growth at transplanting to compensate for root loss is not
necessary for properly pruned, nursery-grown plants. Excessive
pruning at transplanting, according to research, reduces ultimate
plant size and does not aid in plant survival.
As a rule, the central leader of a tree should not be
pruned unless a leader is not wanted, as is the case with some
naturally low-branched trees or where multiple-stemmed plants are
desired. Trees with a central leader such as linden, sweet gum, or
pin oak may need little or no pruning except to eliminate branches
competing with the central leader; these should be shortened. Some
pruning may be necessary to maintain desired shape and shorten
The height of the lowest branch can be from a few
inches above the ground (for screening or windbreaks) to 12 feet
or more above the ground (as needed near a street or patio). Lower
limbs are usually removed over a period of years, beginning in the
nursery and continuing for several years after transplanting,
until the desired height of trimming is reached.
For greatest strength, branches selected for permanent
scaffolds must have wide angle of attachment with the trunk.
Branch angles of less than 30° from the main trunk result in a
very high percentage of breakage while those between 60° and
70° have a very small breakage rate.
Vertical branch spacing and radial branch distribution
are important. If this has not been done in the nursery it can at
least be started at transplanting.
|Scaffold branches of trees should have proper vertical and
radial spacing on the trunk
Major scaffold branches of shade trees should be spaced
at least 8 inches and preferably 20 inches vertically. Closely
spaced scaffolds will have fewer lateral branches. The result will
be long, thin branches with poor structural strength.
Radial branch distribution should allow 5 to 7
scaffolds to fill the circle of space around a trunk. Radial
spacing prevents one limb from overshadowing another, which, in
turn, reduces competition for light and nutrients. Remove or prune
shoots that are too low, too close, or too vigorous in relation to
the leader and scaffold branches.
When deciduous shrubs are planted bare-root,
some pruning may be necessary. Light pruning of roots may be
needed if any are broken, damaged, or dead. The branches of shrubs
should be pruned by the thinning method (covered later in this
chapter), not shearing, to reduce overall plant size by 1/2 or
Shrubs transplanted with a ball of soil or from a
container require little, if any, pruning. Occasionally, branches
may have been damaged in transit, and these should be removed at
the time of planting. Prune only to maintain desired size and
Most evergreen trees and shrubs are sold B & B
(balled and burlapped) or in a container and, as with deciduous
shrubs, require little pruning of branches.
Maintaining Plant Health
In pruning to maintain plant health, first consider sanitation,
which includes the elimination of dead, dying, or diseased wood.
Any dying branch or stub can be the entry point or build-up
chamber for insects or disease that could spread to other parts of
the tree. When removing diseased wood such as a fungal canker or
fire blight, it is important that the cut be made in healthy wood,
beyond the point of infection, with a sterile blade.
The development of a sound framework through proper
thinning will help prevent disease and loss of vigor while
maintaining good form. Even evergreen shrubs usually will benefit
from an occasional thinning of foliage. This thinning will allow
penetration of light and air throughout the shrub, resulting in
even growth of the foliage.
Quality of Flowers, Fruit, Foliage, and Stems
The more flowers and fruit a plant produces, the smaller they
become, as can be seen on an unpruned rose bush or fruit tree.
Pruning reduces the amount of wood and so diverts energy into the
production of larger, though possibly fewer, flowers and/or fruit.
Most flowering shrubs will bloom either on 1-year old growth or on
new growth. Properly timed pruning will increase the production of
wood that will bear flowers.
Some deciduous shrubs have colored barks which are
especially delightful in winter. The best color is produced on
young stems; the greatest stem length and most intense color
results from hard pruning.
Over time, trees and shrubs will often grow to sizes that exceed
the space allowed for them. Where space is limited, regular
pruning becomes necessary to keep plants in bounds. Regular
pruning is necessary on formal hedges to maintain a uniform growth
rate. To reduce labor, select plants that will not exceed allotted
Pruning shears are good for branches up to 1/2-inch in diameter.
Attempting to cut larger branches risks making a poor cut and/or
ruining the shears. There are two styles of hand shears: anvil cut
and scissor action. In the anvil style, a sharpened blade cuts
against a broad, flat plate. In the scissor style, a thin, sharp
blade slides closely past a thicker (but also sharp) blade. The
scissor style usually costs more, but makes cleaner, closer cuts.
Whereas the anvil style, unless very sharp, crushes plant tissue
as it cuts. The pruning wounds take longer to heal.
Lopping shears have long handles and are operated with
both hands. Even the cheapest can cut 1/2-inch diameter material.
The better ones can slice through branches of 2 inches or more,
depending on species and condition (e.g., pin oak is tougher than
linden, and dead wood is tougher until decay sets in
than live wood). Lopping shears also are available in anvil and
scissor types. Again, the scissor cut is better than anvil cut
|Combination Pole Saw-Pruner
Pole pruners have a cutter with one hooked blade above
and a cutting blade beneath. The cutter is on a pole and is
operated by a lanyard pulled downward. The poles can either be in
sections that fit together or telescoping and can be made of
several materials. Wooden poles are heavy. Aluminum poles are
light but can conduct electricity if they touch an overhead wire.
Fiberglass or some type of plastic compound is probably the best
answer. Poles can be fitted with saws, but these are usually very
frustrating to use.
Use of pole pruners can be dangerous, as material cut
overhead can fall on the operator (unless it hangs up in other
branches); exercise caution and wear head and eye protection.
Hedge shears have long, flat blades and relatively
short handles, one for each hand. Heavy-duty shears, with one
blade serrated, are good for difficult jobs. Power hedge shears
are also available. The most common for home use are electric
Fineness of cutting edge is measured in points (teeth
per inch). An 8-point saw is for delicate, close work on small
shrubs and trees. Average saws are normally 6 points, while 4 1/2-
point saws are for fairly heavy limbs.
A fixed-blade saw with a leather scabbard is safer and
easier to use. Folding saws either require a screwdriver (for a
slotted-head holding screw) or will have a protruding wing nut,
which can scar the trunk when a limb is cut. If the saw suddenly
folds while in use, the operator's fingers can be injured.
Blades can be either straight or curved. Many prefer a
curved blade that cuts on the draw stroke. A double-edged saw has
fine teeth on one side, coarse on the other; these can be
difficult to use in densely branched plants.
Bow saws are good only where no obstruction exists for
a foot or more above the area to be cut.
Chain saws come in a variety of sizes, both gas and
electric. However, in general, chainsaws are not appropriate for
pruning live plant material. They are better suited to tree
removal and cutting firewood.
Care of Tools
Clean and oil tools regularly. Wipe an oily cloth on blades and
other surfaces after each use. Keep cutting edges sharp. Several
passes with a good oil-stone will usually suffice. Wooden handles
should be painted, varnished, or regularly treated with linseed
oil. Use tools properly. Don't twist or strain pruners or loppers.
Keep the branch to be cut as deeply in the jaws and near the pivot
as possible. Don't cut wire with pruning tools.