Pruning Mesquite Trees
Mesquites need thinning to reduce chances of wind damage.
Needs early support with stakes. New growth becomes pendulous.
Trim back one third to encourage more vertical growth.
Thin small crossing branches inside of head and prune drooping branches
to head height during summer growing period to relieve foliage density
stress during heavy wind.
Vigorous growth. Substantial tree in 5 to 6 years.
Develops a crown rapidly. Thin inside growth in windy areas to allow wind to sift.
Chilean Mesquite tend to make the best shade trees with a wide dense canopy, fast growth to 25 ft. tall by 25 ft. wide.
However, if they are overwatered and/or improperly staked and pruned they may grow too fast, become top-heavy and blow over.
Thin small crossing branches inside of head and prune drooping branches to head height during summer growing
period to relieve foliage density stress during heavy wind.
In times of adequate rainfall, native stands of mesquite, palo verde
and others are able to grow sufficient leaves to provide a canopy of
shade for branches and trunks. Not so in times of drought. Leaves are
sparse, allowing too much direct sunlight to contact the branch wood.
When this happens, a condition known as "sun-scorch" occurs. The sun's
rays heat the wood to such an extent that the cambium, or sapwood layer
under the bark is burnt and dies. This is much the same process as when
we are overexposed to the sun and our skin becomes sun burnt. But
unlike people, damaged tissue doesn't just peal away and replace itself
with new skin or cambium. The damage is permanent!
Trees suffering from sun-scorch have branches that become cracked, with
patches of pealing bark. Long patches of gray bark develop and are
usually surrounded by a small crack. This is where the dead tissue has
pulled away from the living bark.
Sun-scorch occurs mainly on the tops of branches, where exposure to
sunlight is most direct and intense. It also is most common on branches
that grow horizontally. Such branches are exposed to the strongest
sunlight, beating down from directly overhead.
Secondary infections frequently develop on sun-damaged wood. The most
common is a fungus disease called sooty canker. Spores of the fungus
which happen to land on cracked and damaged bark can germinate and
begin to grow. As the disease develops, a black sooty substance is
formed under pealing bark. The black, soot-like substance is actually a
mass of fungal spores.
Bark beetles and wood boring insects may also attack sun-damaged wood.
The larvae of wood boring beetles tunnel under the damaged outer bark,
and can move into health surrounding wood. There feeding further
destroys the wood cambium.
Branches which have been sun-scorched usually die. As a result, there
are even fewer leaves to protect the remaining branches, and so the
Sun-damaged limbs should be pruned out, back to healthy wood. To
determine where the sun damage ends and healthy begins, scrape the bark
with a sharp knife. If the sapwood underneath is brown and dry, that
part of the branch is dead. If the sapwood underneath is green and
moist, it's alive. Prune the branch back to the main trunk or to a
Reflective paint can be applied to branches that are in a position to
be exposed to strong sunlight. If pruning out of dead or damaged limbs
has further exposed healthy wood to strong sunlight, these limbs can be
painted with a solution of white latex paint to reflect the sun's rays.
Mixing one part white latex paint with nine parts water will create a
white wash that can be applied to the exposed wood. Although a
temporary detraction to the appearance of the tree, the white wash
wares off in time.
To prevent future sun-scorch injury, encourage new leafy growth by
watering effected trees thoroughly. If you have valuable trees,
especially those near your home, not currently on drip irrigation,
consider watering them. One deep soaking every 2 months, from early
spring to early fall will stimulate abundant leafy growth. Watering can
be skipped in the summer, if monsoon rains are adequate.
A light spring fertilization along with a deep watering will further
encourage a leafy tree canopy. Spread ammonium sulfate (21-0-0) evenly
under the branches, at the rate of one-half pound for every 100 square
feet. For instance, a mesquite tree with a 20 feet branching spread
from side to side would cover approximately 300 square feet. This area
then would require the application of 1.5 pounds of ammonium sulfate or
similar analysis fertilizer. Ammonium sulfate is available at most area
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