University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article


Dr. Leonard Perry, Extension Professor
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.

Choose the right tree for the right site, not just a tree you like.  This means it is cold hardy in your area.  It also means it is 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.

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.  Obviously check for signs of leaf injury from pests or diseases, or trunk damage from mishandling.

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.

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.

This issue of planting depth is so important, and such a cause of tree death nationally, that an industry group has been formed to research this and to promote proper planting. They suggest looking at the structural roots as even better than looking at the root flare, as sometimes this can be mistaken for a graft union-- the point at which two different trees are spliced together.

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.  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.

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.

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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