has been said that a tree is not planted until it has been in the
ground five years. This reflects the time required for transplanted
trees to re-establish healthy root systems in the landscape. Proper
care and maintenance are required to keep trees healthy and safe,
especially from external injuries to the tree, which can seriously
harm a tree's health. The best way to care for tree injuries is
to prevent them from happening.
The first and possibly most important steps in injury prevention
are proper selection, placement, and planting of a new tree. Select
trees with well-developed crowns and no wounds on the trunk or branches.
Trees pruned heavily in the nursery or severely wounded in handling
may have serious problems later. Trees should be planted in shallow,
wide holes to allow rapid root growth after planting. Planting trees
too deep is a common problem. Look at the site carefully and completely.
Is the space large enough to accommodate the mature tree's crown
is an important maintenance practice for trees. However, an epidemic
of over-mulching is plaguing many managed landscapes. Properly applied
mulch increases growth rates, prevents basal damage, and conserves
soil moisture. Organic mulch such as wood chips or bark should be
applied around the tree to a depth of two to four inches. Mulch
should be spread a foot or more from the base of the tree in all
directions, but never to a depth of more than two to four inches.
Mulch can be placed directly on grass when mulching established
trees. Monitor mulched areas during the winter to detect any rodent
activity. Mulch should be renewed as needed to keep a constant layer
around the tree. Avoid using rocks or plastic sheeting to protect
the tree--rocks cause soil compaction, and plastic sheeting suffocates
weed barrier fabric can be effective at reducing weed competition,
allowing moisture and oxygen to enter the soil around the tree.
It does not, however, add organic matter to the soil or reduce compaction
like a natural mulch.
Moisture is critical to trees, but too much moisture can cause serious
damage. Newly planted trees should be watered once per week (1 inch)
in the absence of rain. Established trees should receive 1 inch
of water every 10 to 14 days. These amounts are in addition to the
water a surrounding grass lawn would need. A new tree in competition
with a surrounding grass lawn may need 2 inches or more of water
a week to thrive.
watering causes a lack of soil oxygen, smothering roots. It can
reduce the number of deep roots. Larger amounts of water should
be applied once or twice a week instead.
with a hose or coarse-droplet sprinkler at a rate low enough to
keep water from running off. Most tree roots are not very deep (within
the upper 6 to 12 inches of soil), and deep roots will receive water
if enough is applied to the soil surface.
trees only when necessary. If growth is adequate and steady, foliage
appears healthy and there has been no major disturbance around the
tree, no fertilization is needed.
fertilizing is necessary, slow release, balanced, granular fertilizer
or soil-applied liquids should be distributed over the tree's entire
root zone. Applying fertilizer through holes augered into the soil
or with fertilizer spikes is not recommended. Routine trunk injections
of fertilizers into healthy trees are not recommended.
tree has different pruning requirements. Here are some important
considerations in minimizing tree damage when pruning or dealing
Target Pruning: When pruning trees, it is important to make
final cuts at the proper location. Cuts should be made from just
outside the branch bark ridge (readily visible on most species)
to just outside the swollen branch base or branch collar. A cut
between these "natural target" points removes all branch tissue
but does not cut into trunk wood.
stubs leads to unwanted sprouting and decay of the remaining stem
tissue. Cuts made too close (flush cuts) leave much larger wounds
than proper cuts and can cause dieback of the surrounding cambium.
As a result, flush cut wounds do not heal properly, causing major
damage to the trunk from which the tree may not recover.
over-pruning trees. Prune lightly once a year for several years
rather than heavily all at once. A good rule-of-thumb is to prune
off no more than about 25 percent of a tree's foliage in one year.
Also try to avoid having to prune branches that are over one to
two inches in diameter. Tipping branches usually causes more problems
later on--it is better to remove entire branches back to the trunk.
branches when they are small makes smaller wounds that close quickly.
When branches die, they should be pruned back to the nearest live
branch, and no stub should be left. Take care not to injure the
branch collar or any callus that may have formed since the branch
Pruning: Trees should not be pruned unless there is good reason
for pruning. Reasons may include safety, removal of dead or injured
branches, correction of a structural defect, or interference with
utility lines. Removal of healthy branches to "thin" a crown or
for similar reasons is never necessary. Topping trees or stripping
live branches from inside a tree are dangerous practices that can
severely impair tree health and longevity.
-- Compartmentalization Of Decay In Trees -- is a concept used to
describe the reactions that take place in a tree in response to
wounding. When a tree is wounded, it sets up defensive walls against
the invasion of decay fungi and other microorganisms. The vessels
near the wound are plugged with gums, resins and chemicals that
resist the spread of decay. The living tissues outside the wounded
area then begin to form a callus layer in an attempt to close the
wound. A properly made cut results in a doughnut-like ring of callus
forming all the way around the wound. Wound closure for small wounds
may take only a few months. Larger wounds may take years to close,
or may not close at all.
Use of Mowers and Other Yard Equipment: Trees often are wounded
by careless use of yard equipment like mowers, weed whips, and other
trimming equipment. These injuries cut through important vascular
tissue just inside the bark, which can lead to decay and ultimately
death of the tree. A bed of natural mulch around the tree eliminates
the need to trim or mow close to the tree's base. Extreme care should
be taken when digging up or tilling the soil under a tree. Many
large and small roots will be cut by such digging, especially if
it occurs close to the trunk.
and Excessive Change in Soil Grade: Trenching next to trees
cuts major roots. Where possible, tunneling should be used to leave
the upper 18 inches of soil undisturbed. When tree roots must be
cut they should be cut cleanly. Ripping or tearing tree roots with
a backhoe or other implement leaves large open wounds or may shatter
roots, preventing the formation of new roots.
in soil grade can seriously injure trees. About 90 percent of the
tree's root system lies within the upper 18 inches of the soil.
Covering tree roots with as little as 3 inches of soil can cause
damage by suffocating roots. Filled areas should be properly tiled
and graveled to allow for air movement and drainage.
Damage: Animals can cause wounds, especially on smaller trees.
Field mice (voles), rabbits, squirrels and deer commonly feed on
the young bark of trees during the winter when food sources are
scarce. Animal damage can be prevented by excluding the animals
from the area around the tree. This can be done with a simple wire
fence around the tree or yard. Discourage rodents by using a plastic
tree guard around the trunk. Check yearly to ensure that the guard
is not girdling the trunk.
Insect Damage: Insects can cause several types of wounds
to trees--some bore directly into the main stem and branches, others
feed on young shoots and leaves. Inspect trees regularly for signs
of insect damage. When damage is noted, take care to identify the
problem properly and use appropriate controls.
Cavities and Drainage Tubes: Cavities in trees require only
minimal care. Clean out any loose wood or debris. Check the cavity
for carpenter ants or termites. These insects should be controlled
not fill the cavity, but rather allow it to remain open. Do not
scrape the inside of a cavity to remove dead wood. This may expose
live tissue and re-wound the tree, allowing decay to spread.
tubes should not be used in trees. Drilling holes to drain water
from interior cavities opens a path for new decay.
Wound treatment should be confined to removal of loose bark or wood.
Leave the wound exposed so the tree may begin the natural process
of callus formation and healing or sealing over. "Scribing" a wound
in an elliptical shape once was recommended to help water and nutrients
flow around the wounded area. This is no longer recommended since
it only makes wounds larger and does not improve sap flow.
Dressings: Wound dressings are not recommended for any tree
wounds. Wound dressings actually have been found to increase decay.
Wounds should be left exposed to the open air to seal naturally.
Injections and Implants: Some insects, diseases and nutrient
deficiencies can be controlled through the use of chemical injections
or implants. These measures, however, require drilling holes into
the trunk and should be used only after all other available treatments
have been considered. Since injection holes are wounds, they should
be made in accordance with manufacturers' recommendations to minimize
the damage they cause. Injection holes should be kept as small and
as shallow as possible and injection should not be repeated more
than once every two or three years, except in severe cases.
Injection points should not be filled or treated with wound dressing
and Bracing: Trees that have severe structural defects or that
have suffered serious damage sometimes can be saved by cable and
bracing techniques. In all cases cable and bracing should be done
by a professional arborist who is familiar with this technique.
Not only can improper cabling or bracing result in damage to the
tree, it can also be very dangerous.
Identification: Trees that have large, dead branches or show
signs of interior decay should be inspected by a professional forester
or arborist. These trees can become major liabilities if left standing.
Accidents can often be prevented through proper pruning. Tree work
can be dangerous, and many tasks should be left to professional
from Dave Mooter and Mike Kuhns, Nebraska Extension, 2000