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PLANTING HOLE
EXCAVATION:
The planting hole should be 1 to 2 inches shallower than
the height of the container being planted with the
bottom of the box sitting on level, undisturbed soil
(Figures 1,2 and 3). This depth keeps the root ball from
settling deeper into the ground and possible causing the
crown (the transitional tissue between the roots and
shoot of the tree) to become buried. Where practical,
the width of the hole should be 3 to 5 times the width
of the container. Fracturing the soil 3 to 5 times the
width of the container is also applicable and more cost
effective (Figure 4 and 5). This large area of disturbed
soil will be more easily penetrated by water and roots,
leading to a dispersed, well distributed root system.
BACKFILL:
Do not add organic amendments (mulch, peat moss,
compost, manure) to the backfill soil. Refill the
planting hole with the soil removed during excavation
creating a profile of soil essentially identical to the
surrounding soil (Figure 6). Remove all but the top most
metal strap from the box before backfilling (Figure
7,8,9,10 and 11). Backfill planting hole about 2/3 to ¾
of the way to the top of the box before removing the top
metal strap (Figure 12 and 13). Remove box sides (Figure
14 and 15). Pack backfill soil to eliminate air spaces
and to further secure the tree in the ground (Figure 16
and 17).
Chemical fertilizers should be applied to the surface of
the soil and "watered-in." A temporary tree well will
help contain post installation irrigations allowing soil
to settle and fill any remaining air pockets in the
backfill (Figure 18 and 19). Once final grade is
established (Figure 20), mulches (wood chips, compost
and decomposed granite) can be applied to the surface of
the soil to reduce evaporation of water from the top
layer of soil. During hot spring, summer and fall
months, when soil temperatures are high and water
content is very low, pre-soak the sides and bottom of
the planting hole before setting the tree in the hole.
With a hose, run water into the planting hole while
backfilling, moving the hose repeatedly to saturate and
cool the backfill mix. Watering while backfilling will
assist in settling the soil and eliminating air pockets.
Tamp and pack backfill soil as described above.
IRRIGATION: SET-UP AND SCHEDULES
Irrigation systems must be flexible enough to meet the
immediate water needs of freshly transplanted tree and
that same tree at maturity. As trees grow the irrigation
system must expand to deliver water over a larger area
beneath the tree. Limited numbers of immovable emitters
produce a physically restricted root system and tend to
keep the soil nearest the trunk saturated during and
immediately following irrigations. These two conditions
can make trees more prone to wind throw.
One alternative arrangement is to install concentric
rings (see diagram 1) of emitters that extend out to the
drip line of the tree. Such an arrangement would
distribute water over a much larger area and result in a
more highly dispersed root system. A second alternative
would be to arrange 13 emitters in an X pattern
(Diagram1) rather than the rings. In either
configuration, the emitter(s) nearest the trunk acts to
help settle, compact and firm the soil around the
freshly transplanted root-ball. Shortly after
transplanting this emitter should be closed or capped
and those near the drip line, if not already open,
should be opened. The capping of this emitter allows the
soil nearest the trunk to dry out and will help avoid
wind throw. The emitters watering the soil profile near
and beyond the drip line will be irrigating the newly
developing feeder and anchoring roots. This management
approach encourages greater root distribution and a
larger total root mass.
WATERING GUIDE
The frequency of tree irrigation will depend on soil
type and texture, maturity of the tree, and the time of
year (day and night temperatures). Sandy, more porous
soils will require more frequent application of water
than will loamy and clay bearing soils. The length of
the irrigation will depend upon the number of emitters
and the volume of water per hour they deliver, the
growth stage of the tree and the time of year.
Immediately following transplantation trees have the
same root mass they had when in the container and should
be irrigated as if they were still containerized. During
this transition, irrigation schedules should be
appropriate to the season and the limited distribution
of the roots. Depending on the time of year it may take
several weeks or even months before the roots of
transplanted trees explore beyond the original growing
container. Post installation irrigation must take into
account the soil type and drainage characteristics, day
and night temperatures, relative humidity, other
potential sources of water (lawn irrigation, rain
gutters, general site drainage) and the differing
tolerance of desert tree species to saturated soils.
Trees watered using a hose must be watered regularly,
frequently and slowly.
For further information on watering, The Desert
Botanical Garden, Phoenix, Arizona, has developed a
useful watering guide that can be accessed from our web
site
www.aridzonetrees.com or from their web site
www.dbg.org
STAKING:
Not all trees require staking when transplanted. Tree
stakes serve two purposes: 1) to help the tree resist
severe winds until the roots become established; and 2)
to direct the trees growth. For these reasons staking
details should allow trunks to sway with milder winds
(this movement stimulates thickening and taper) yet
provide protection from uprooting in wind.
Rounded wooden stakes, two inches in diameter are most
commonly used. Stakes should be long enough to allow
them to be driven into undisturbed soil yet leave enough
wood above ground to adequately secure the trunk. The
numbers of stakes recommended ranges from 2 to 4 with
two for single trunk trees and three to four for
multiple trunk trees (Figure 20). When two stakes are
used, an imaginary line drawn between the two stakes
should be at right angles to the most critical winds.
For multiple trunk trees set stakes evenly in a
triangular arrangement to the outside of the trunks.
Again with multiple trunk trees, allow movement of the
tree perpendicular to the prevailing winds. Natural
multiple trunk (bush form) do not require staking.
Ties connect the tree trunk to the stakes and are
typically arranged opposite one another to provide
support yet allow give, this configuration also keeps
the trunk from being injured by hitting the stakes
(Figure 21). Material used as ties varies from wire
inserted through plastic tubing or pieces of garden hose
to tree tape. Typically arranged in a figure eight
looped between the stake and the trunk, ties should be
flexible and secure. Once staked trees are established,
supporting materials and ALL ties should be removed to
prevent future damage to trees. Failure to remove ties
can cause girdling of the branches and trunks they are
attached to. Staking should not be a standard practice
applied to all newly transplanted trees.
POST-INSTALLATION PRUNING
Pruning immediately following installation reduces the
tree's capacity to photosynthesize and only serves to
slow new root, stem and leaf growth and can delay tree
establishment. Such pruning is considered unnecessary
and potentially detrimental. Prune only broken or
damaged limbs. Selecting trees with form and structure
that are appropriate for the particular landscape
setting should reduce the need for significant pruning
following planting. Follow the 80/20 pruning guideline
(see below) whenever you prune.
POST-INSTALLATION FERTILIZING
Applying fertilizer formulations that contain nitrogen
and phosphorous immediately following transplanting, in
either granular or liquid form, promotes rapid
vegetative growth and contributes to new root
development (Figure 21). In nutrient poor soils it may
be desirable to use a formulation adding potassium
(Potash) and micronutrients. When using dry fertilizers
the best results are with homogeneous formulations. In
these formulations each granule of product has the same
nutrient concentration (e.g. 20% N, 20% P and 20% K).
Blended NPK fertilizers (e.g. 20-20-20) are separate
nitrogen, phosphorous and potassium granules mixed
together. To provide nutrients for both existing and
developing roots distribute fertilizer uniformly beneath
the leaf canopy from the trunk to just beyond the drip
line. Irrigate generously following application to allow
fertilizer to penetrate into the root zone. Fertilizers
applied in the cooler months, when little if any tree
growth occurs, have no immediate effect on
establishment. An application at bud break is
recommended. Read and follow the recommended
application rates and re-application intervals listed on
the package for the specific fertilizer product used.
PRUNING ESTABLISHED TREES
Periodic light thinning is the most desirable method of
pruning. Light thinning, especially important in June,
July and August can reduce the number of wind-damaged
branches and prevent uprooting of trees. Removing large
portions of the tree canopy (more than 30%) during any
one pruning session in the summer growing season, can
lead to aggressive, unwanted re-growth, limited root
development and increased vulnerability to sunburn
injuries that can be colonized by wood boring insects.
No more than 20% of the tree foliage should be removed
at any one time with 80% of this pruning concentrated on
the new growth on the outer third of the canopy. Limbs
pruned from this area should be no larger than about ½
inch in diameter and should require only hand pruners to
remove. The remaining 20% should be pruned from the
inner two thirds of the canopy removing succulent
("water") growth and crossing branches. Crossing
branches or succulent growth should be removed from this
inner 20% periodically throughout the growing season as
some of these "temporary" branches serve to help
permanent branches develop caliper, taper and greater
strength.
Avoid hedging or heading back desert species, as this
will only stimulate excessive branching. Some desert
species are slow to exhibit the effects of freeze
damage. Branches that do not immediately produce leaves
in spring may not be damaged. Delay pruning suspect
branches until the tree has begun producing new leaves.
Realize that early season pruning can reduce spring
flowering. Always use clean, sharp tools that are
regularly cleaned in a fresh 10% solution of bleach and
periodically sharpened. Bleach acts as a sterilizing
agent and help prevent the spread of diseases within and
between trees being pruned.
FERTILIZING
ESTABLISHED TREES
The majority of arid landscape trees have evolved in,
and are well adapted to, nutrient poor soils. The lack
of rainfall and the limited availability of nutrients
serve to moderate the growth of trees in the native
Sonoran desert. Water and fertilizer are effective tools
for managing tree growth and overall health of desert
trees in landscapes. When trees approach or reach the
desired size, reducing or eliminating the application of
nitrogen and irrigation will slow or moderate growth.
Slower growth of maturing trees limits the severity of
branch damage from summer wind storms, reduces the risk
of wind throw, and limits the amount of annual pruning
required. Late summer and early fall applications of
nitrogen can encourage late season vegetative growth
that is more vulnerable to freeze injury in winter.
Read and follow the recommended application rates and
re-application intervals listed on the package for the
specific fertilizer product used.
Printable copy click
Tree Planting Practices an Overview PDF file

Figure 20.
Ties connect the tree trunk to the stakes
and are typically arranged opposite one
another to provide support yet allow give.
Ties are padded where they contact the
tree's bark to prevent injury and damage.

Figure 21. To provide nutrients
for both existing and developing roots
distribute fertilizer uniformly beneath the
leaf canopy from the trunk to just beyond
the drip line. Irrigate generously following
application to allow fertilizer to penetrate
into the root zone. |
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Figure 1. Select tree with a form and shape
that compliments all the use of the landscape and does
not adversely impact surrounding plant material, turf,
pedestrians, signage, or hardscape elements. Solid line
indicates planting hole, broken line indicates area of
fractured soil.

Figure 2. It is not necessary to remove the
bottom of the box. The bottom of the box should sit on
undisturbed soil and the crown of the tree should be
about 2" to 4" above the finished grade.

Figure 3. Leaving tree slightly above grade
insures that if rootball settles that crown will remain
at or above grade.

Figure 4. Where it is not cost effective to
dig a wider planting hole, fracture soil to promote root
development.

Figure 5. Fractured soil improves water
penetration and root distribution.

Diagram 1. Arrangement of irrigation emitters
in a concentric pattern, starting at the trunk and
extending to the edge of the leaf canopy.
Click for Printable PDF copy.

Figure 6. Back fill with the soil removed from
the hole to create a good interface between the rootball
and the surrounding undisturbed soil.

Figure 7. Cut bottom band first.

Figure 8. Cut the middle band second.

Figure 9. Cut vertical
bands next.

Figure 10. It is not necessary to remove the
bottom of the box.

Figure 11. Cut the top most band last.

Figure 12. Remove strap.

Figure 13. Remove box sides, one at a time.

Figure 14. When all 4 are removed, complete
backfilling the hole.

Figure 15. Using the shovel handle,
periodically tamp the backfill to remove air pockets.

Figure 16. Continue compacting the backfill
until you reach the finished grade.

Figure 17. Set-up a temporary tree well for
the initial 1st and 2nd deep irrigations to help further
settle the back fill.

Figure 18. Deep irrigations allow surface
applied fertilizer to penetrate into the rootball.

Figure 19. Grade down temporary tree well
exposing root-ball 1-2 inches above grade for top
dressing with mulch/decomposed gravel. |