University of Vermont
Department of Plant and Soil Science

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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 peach tree!
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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