University of Vermont
Department of Plant and Soil Science
Spring, Summer News ArticlePLANTING TREES CORRECTLY
Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont
Yes, there are right and wrong ways to plant a tree. By following
correct planting practices, you can ensure trees will avoid a slow
decline and possible death from several causes. This is especially
important for trees, which can be a large, long-lasting, and
worthwhile landscape investment.
Choose the right tree for the right site, not just a tree you like.
This means that it will be cold hardy in your area. It also means
that it will be adaptable to your soils and site. A sugar maple
near pavement and buildings may dry out with leaves turning brown,
or show salt injury if near roads. A pine tree will grow poorly on
a heavy clay soil.
Consider trees for their function. Perhaps it is just the beauty of
a spring crabapple in bloom, and the fall fruits it produces for
birds. Native trees provide the thousands of insects that birds
feed upon. Picking fresh fruits from your trees provides incredible
taste and nutrition, plus saves money over buying them. Of course
trees can be used for windbreaks and summer shade.
Choose a healthy tree. This is one that has a good amount of roots
in proportion to the tops. Beware of trees that have been recently
dug from the wild with little or no preparation prior to digging.
Often you get what you pay for. Obviously check for signs of leaf
injury from pests or diseases, or trunk damage from mishandling.
Local nurseries with trained professionals are your best bet usually
for buying healthy and appropriate trees.
Beware of trees sold in many large national chain stores. These
usually have been grown in distant areas, and may not be acclimated
to our area. I have found ones at such stores with few roots, the
pots containing stones to hold the plants upright. If in doubt,
gently pull the plant out of the pot and look at the roots. If
non-existent, too few roots, too small pot and root size for the
plant top, or the plant is pot-bound, keep looking.
Particularly early in the season, before trees are leafed-out or in
bloom, it is hard to tell if they are labelled properly. One time I
saw a tree labelled as a crabapple at a chain store, only to see a
few weeks later when leaves were out that it instead was a non-hardy
If you get home with a balled and burlapped tree and, once
unwrapped, see girdling roots, either take the tree back or talk
with your source. Girdling roots are those that are growing around
the base of the trunk and, as they grow, basically end up strangling
the tree over time. They are a sign of poor culture in the nursery.
When digging the planting hole, measure the width of the root mass
(root ball) and remove sod in an area three to five times the
diameter of the root ball. Loosen this soil to a depth of about a
foot, such as with a spading fork. Then dig a hole in the center of
this area about a foot wider than the root ball.
If planting a potted tree, of course remove the pot. If a fiber
pot, you can cut it off with pruners or a knife. If planting a
balled and burlapped tree, remove any strings holding the burlap,
once the plant is in the hole. Remove any wire with wire cutters.
Even though burlap will decompose over time, it won’t if it’s
treated. Best is to remove any burlap, again once the plant is in
the hole, cutting it off. If the soil on the outside of the
rootball is compacted or roots are crowded, tease them loose with
pruners or similar hand tool such as a planting knife. Cut away any
roots circling the surface around the trunk.
Planting depth is one of most important factors in planting.
Planting a tree too deep can kill it. Figure the depth to plant by
pulling any soil away from the trunk. What you are looking for is
the root collar or root flare-- the bulge just above the root system
where the roots begin to branch away from the trunk. This root
flare should be just above the soil surface, the base of the root
flare at the soil surface. This often may not be the top of the
root ball, hence the need to make sure.
Measure from the base of the root ball to the base of the root
flare. This is the depth to plant. Don't dig the hole deeper, as
some instructions in the past or older books may indicate. Either
the tree will be too deep to start or, if you backfill with soil,
the tree will settle lower and end up too deep.
Don’t mistake the root flare with the graft union on some trees,
particularly many fruit trees. This is the point at which two
different trees are spliced together, the desired tree on an
“understock” to provide traits such as vigor and hardiness. If you
suspect a graft union, but aren’t sure, again check with your source
or a local nursery with trained professionals. A graft union will
resemble a swelling or bump on the stem, compared to the flared base
of a standard tree trunk. Plant grafted trees with the graft union
two- to four-inches above the soil surface.
Absence of a root flare near the soil surface is a sign the
structural roots are too deep and need to be planted nearer to the
surface. Structural roots are the large woody roots from which all
the finer roots branch. Measured about four inches from the trunk,
these should be no more than three inches deep. You can find these
by probing with a long thin object. Many nursery trees have few
structural roots, and these may be much deeper than three inches in
the root ball.
Another misconception from the past is that you should amend the
backfill soil. This promotes roots staying in the better
environment you've created in the planting hole. This in turn
promotes girdling roots. The recommendation now is not to amend the
backfill soil, choosing the right tree for the right soil instead.
Amend only if the soil is very poor, such as severely disturbed
soils with rubble from construction.
If you have removed soil from the trunk base to expose the root
flare, this trunk tissue may be more susceptible to cold or sun
injury. If such is the case, replace with a mulch but do not mulch
too deep. This is another cause of tree injury, and is often
referred to as "volcano mulching" from its appearance. If you
haven't excavated near the trunk, keep mulch away from it. Only
mulch about two inches deep, uniformly around the planting area.
When planting, you may create a shallow basin away from the trunk to
hold water, and water well. Keep the tree watered well for the
first season if there isn't sufficient rain. It is better to water
deeply, less often such as once a week, than just a little every
day. If it is difficult to get water to trees, you can use a tree
watering bag or “donut” ring that you fill with water, fit around
the tree, and they release water slowly. You often see these in
commercial landscapes, and can find them for sale at complete garden
stores or online.
Other practices to follow for a healthy tree:
--Don't fertilize at planting time.
--Prune only injured branches. Don't paint tree wounds.
--Remove any tree wrap or tape around trunks. This only should be
used for protection in transit.
--Don't stake trees unless necessary in very windy areas, or to
prevent vandalism. If you do stake, use sturdy stakes and attach the
tree with wide strapping or tree roping. Normal twine can cut into
the tree bark.
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