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Planting
Landscape Trees
by Michael Kuhns, Extension Forestry Specialist
Trees and shrubs are a valuable addition to most property, providing
beauty, wind protection, shade, wildlife habitat, visual screening,
and other benefits. Unfortunately, many landscape trees are not
properly planted or cared-for. In this publication we describe up-to-date,
research-proven techniques for planting landscape trees and for
post-planting care. For a more complete description of selecting
and planting landscape trees click
here.
Tree Type
Landscape trees and shrubs can be obtained in three basic types:
bare-root, balled and burlapped, or container plants. Each type
has its own advantages and disadvantages and none is ideal for all
situations. With all three types you need to be sure that you have
an adequate root system--a good rule-of-thumb is that the root system,
root ball, or container diameter or spread should be 10 inches to
12 inches for every inch of stem caliper (diameter at ground-line
just above any basal swell). Therefore, a 3 inch caliper tree should
have a 30 inch to 36 inch wide root ball as a minimum. Root ball
depth is not as critical as width but should be larger for larger
trees.
- Bare-Root
-- Bare-root plants are dug with no soil around the roots and
may only have a few coarse, woody roots attached. They are inexpensive
and light weight, but they can be difficult to find and their
exposed roots must be kept moist. Bare-root deciduous trees should
have a caliper smaller than 2 inches and bare-root evergreens
should be very small (less than 2 feet tall). Bare-root trees
should be planted only when they are dormant and spring planting
is best.
- Balled and Burlapped-- Balled and burlapped (B&B)
plants are dug with a ball of soil intact around their roots.
The root ball is tightly wrapped with burlap held in place with
twine, nails, and possibly a wire basket. More roots are contained
in the root ball so transplant shock is reduced. Rough handling,
though, can break roots and make them lose soil contact, so handle
these trees with care. B&B plants are much more expensive
than bare-root trees and are much heavier but generally have a
better chance of survival.
- Container Plants -- Trees are sometimes grown and sold
in pots of various types and sizes for convenience and to avoid
root loss during transplanting. Container-grown trees are normally
more expensive and heavier than bare-root but less than B&B.
Round pots can cause roots to circle which can cause girdling
roots later in a tree's life. Such roots should be cut or straightened
at planting time. Container trees should be well-rooted without
being root-bound. Also avoid buying bare-root trees that have
recently been potted and are not well-rooted. Such trees may transplant
well but are more expensive than they are worth.
- Tree Spaded -- A tree spade, a large machine that cuts
roots and soil so the root ball can be wrapped, is often used
to dig B&B trees in the nursery. Some landscape contractors
also move trees to the site and transplant them into a previously
dug hole with the tree spade. These trees can be treated similarly
to a B&B tree, but take care to make sure that the gap between
the root ball and the hole is closed so roots can grow out. Tilling
around the root ball, as mentioned under B&B trees, is a good
way to ensure good contact between the root ball and soil.

Trees can be obtained from nurseries and garden centers as
bare-root stock, balled-and-burlapped stock, container grown, or
tree-spaded (not shown).
Tree Planting
- Digging the Hole -- Dig your planting hole much wider
than the root ball with sloping sides; a hole at least 3 times
the root ball width is best (see diagram). The hole should be
just deep enough so the bottom of the root ball can be placed
on undisturbed soil and the root collar will be at or above the
level of the surrounding soil. The root collar is a flared or
swollen area on the trunk where the root system and trunk meet
and where the soil contacted the trunk in the nursery. Loosening
the soil in the bottom of the hole has been recommended in the
past but this lets the heavy root ball settle and sink, causing
the tree to be too deep. The sides of the hole may become glazed
and smooth during digging if the soil is clayey and moist, making
root penetration difficult. If this occurs, roughen the glazed
surfaces and open up the soil's pores and cracks by picking at
the soil with the tip of the spade or a trowel.
- Placing the Tree -- Place the tree in the bottom of the
hole onto undisturbed soil with its stem vertical. Handle the
tree by its root ball or container to avoid trunk damage. Never
drop the tree or you will loosen the root ball and break roots.
Make sure that the root collar is at or above the surrounding
soil grade. Be careful because many trees have been coming
from nurseries with their root collar actually buried deep in
the root ball. Planting such a tree with the assumption that the
root collar is at the top of the ball will result in a tree planted
too deep. If the root collar on your tree is buried a few (4 to
6) inches deep in the ball, just remove the extra soil on top
of the roots and plant. If the root collar is deeper than that
consider returning the tree, since much of the root system likely
is missing.
Now start to remove packing materials from the root ball.
Ropes and wires that surround the trunk or root collar should
always be removed or they will eventually girdle the tree. Roots
must quickly grow from the root ball into the surrounding native
soil for the tree to survive. Though untreated burlap breaks down
fairly quickly in the soil, treated burlap and some types of pots
break down too slowly to assure good, quick root growth out of
the root ball. Therefore, if the root ball or potted root system
is strong and firm all packing materials should be removed, including
pots, wire baskets, and burlap. If the root ball is broken and
loose, remove these materials carefully and only to the extent
that you can keep the root ball together. Backfilling as you remove
these materials may help keep the root ball intact.
Any burlap or potting material that must be left on should be
slit in several places to allow roots to grow through. It is less
important but still desirable to remove packing materials left
underneath the root ball. Cleanly cut any circling or damaged
roots that are exposed at this point to promote good root growth.
Place bare-root trees with their root collar positioned as mentioned
above and with their root system spread out in the flat-bottomed
hole or over a shallow mound constructed in the bottom of the
hole. Do not bend or kink roots to make them fit. If roots are
too long for the hole either dig the hole wider and deeper or,
as a last resort, cut off some root length with sharp hand pruners.
Also cleanly cut any crushed, torn, or otherwise damaged roots.
- Backfilling -- Fill the hole with the original native
soil--this is the soil the tree must ultimately move its roots
into in order to survive. Large rocks can be removed when backfilling.
Up to 25% by volume of composted organic matter can be mixed in
with the backfill soil if it has a very high clay content and
is difficult to work. Otherwise use no other soil amendments.
Polyacrylamide gels (water absorbing polymers) added to the backfill
at planting time have been shown to have no significant effect
on tree survival or growth.
Break up large clods as you backfill and pack the soil occasionally
to remove air pockets. Pack the soil with your hand or lightly
with your foot to avoid over-compaction. Straighten the tree and
keep its root collar at the right level as you backfill. Add and
pack the soil until it is even with the surrounding soil level
and the root collar. If you are purposely planting the tree shallow,
mound the soil up to the root collar. No roots should be exposed
when backfilling is complete. Water well immediately after backfilling
to help settle the soil and remove air pockets. Additional soil
can be placed where settling occurs but no packing should be done
after the soil is wet.

The planting hole should be shallow and wide to allow for rapid
root growth after planting. Planting trees too deep is a common
problem.
- Planting With Poor Drainage/Compaction -- Poor drainage
can and should be improved if possible by grading or installing
drain tiles to carry water away (see diagram). On flat sites or
sites with moderate drainage or compaction problems trees can
be planted shallow, with one-third or more of the root ball above
grade and the backfill soil mounded up to cover the root system.
Trees can even be placed on top of the existing, problem soil
with their roots surrounded by a mound or berm. Such trees may
do well but also may have a fairly small root system and will
need more care and attention than trees on better sites.

Where adequate drainage is a problem, either elevate
part of the root ball above grade and gradually slope the soil around
it (see above) or provide a drain to a lower point (see below).

- Season to Plant -- Trees are best planted when they are
still dormant with tight, unopened buds in the early to mid-spring
after the soil has thawed. Moderate temperatures and good soil
moisture in the spring help trees get established. Fall planting
also works well for many species, though watering will be critical
if the fall is dry. Summer planting of B&B and container plants
can be done successfully, though hot temperatures, dry conditions,
and non-dormant trees makes good care especially important and
survival less sure. Bare root trees should only be planted in
spring while still dormant.
Follow-up Maintenance
- Water thoroughly at planting time and for a year or two after
transplanting until a good root system is established. Water not
only should be applied to the planting area, but also to the soil
surrounding the hole so roots can grow out. Remember, it is possible
to over water a tree, especially in poorly drained soils. All
landscape trees should be watered regularly during periods of
severe drought.
- Do not fertilize at planting time since fertilizers decrease
root growth and can cause the crown to outgrow the roots. No hormones,
extracts, vitamins or other such formulas have been shown to stimulate
root growth or help tree establishment. Fertilizing should only
be done after the tree has recovered from transplanting, and then
only if needed. This recovery can take two or three years; longer
with larger trees.
- Mulch with wood chips or other coarse organic material around
the base of newly planted and existing trees to increase root
and tree health. Mulch should extend several feet from the trunk
(wider is better), should be 3 to 4 inches deep, and should be
renewed as it breaks down. Keep mulch a couple of inches away
from the base of the trunk to avoid root or trunk decay. Air tight
plastic sheeting and rock beds should not be used around trees.
Porous weed barriers of woven or matted plastic can provide effective
weed control but can be difficult to install and maintain and
are not much more effective than an adequate organic mulch layer.
- Stake newly planted trees only where wind is a problem. Guy
loosely to allow some stem movement, using canvas strapping or
similar materials around the tree to prevent trunk damage; hose
covered wire often girdles trees. Remove all staking materials
after one or two years. In heavily used areas the presence of
a couple of tall stakes may help to physically protect the tree
even if no guying materials are used.

Staking varies with tree size. Use one stake for
trees up to 2" in diameter (A), two stakes for trees 2-4"
in diameter (B), and at least three stakes for trees over 4"
in diameter (C). Wires can be used, but materials that contact the
trees should be soft and flexible, like webbing or rubber straps.
- If you wrap the trunk of your new tree, wrap corrugated paper
or other material from the base to one-half of the way up the
trunk, overlapping as you go and using masking tape at the top.
Apply wrap in the fall after leaf drop and remove each spring,
repeating for no more than two or three years. Do not wrap trees
with trunks that will be shaded in the winter. Recent research,
however, has shown that wrapping trees may do as much harm as
good.

Trunks of newly planted trees can be protected with a special
tree wrapping paper. The paper is wrapped in overlapping layers
starting at the bottom and working up to the branches.
- Prune dead, diseased, damaged, or rubbing branches at planting
time. Do not "head back" at planting time to "balance"
the roots and crown, as this only weakens the tree. Branches that
are too low or are otherwise poorly located can be removed in
a year or two when the tree has had a chance to recover from planting.
- Control weeds by using a wide mulch bed several inches deep
and by pulling weeds or using directed sprays of herbicides as
needed. Herbicides or weed killers that are taken up by roots
should not be used since they may harm the tree. Keep all weed
killers off of tree leaves, young bark, and sprouts coming from
the tree base.
For More Information
There are many good sources of information, including your local
Cooperative Extension office, the library, your local nursery or
garden center, or a local arborist. Be sure that your source of
tree information is up-to-date and is familiar with the latest research
on landscape trees. Much of what was recommended for trees in the
past has turned out to be unnecessary or even harmful to trees,
so remaining current is very important. For general information
related to landscape trees or community forestry contact the Utah
Community Forest Council, Box 961, Salt Lake City, Utah 84110-0961.
Some of the drawings in this article are from "Selecting
and Planting Trees" published by the Morton Arboretum, Lisle,
Illinois, and are used with their permission.
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