How Deep Should You Plant a Tree?

When you plant a tree, you want to ensure that it won’t lean or fall over so you should plant it deeply, right? Wrong! It may surprise you to learn that planting too deeply is one of the primary causes of premature tree death. Instead, trees should be planted so that the root flare at the base of the tree is above ground. Keep reading to find out why and how to properly plant a new tree at the right depth.

Why is the Root Flare Important When Planting a Tree?

Exposed root flare showing previous soil level on a tree trunk that was planted too deeply.

The root flare, or trunk flare, was buried when this tree was planted, leading to issues as the tree grew.

Root flare, also called trunk flare, is extremely important to a tree’s health. The root flare is found at the base of the trunk where the tree’s trunk ends and the root system begins.

Often roots develop about 12 inches below the soil line, which is just below the tree flare. Root flare depth is important. Trunk tissue surrounding the root flare, the phloem, can rot if it receives too much moisture. Phloem is an important part of a tree because it helps in the manufacture of energy for foliage production. Burying the root flare or piling it high with mulch when planting a tree can encourage the rot of the phloem.

>> Read more about how you can prevent expensive tree problems here.

What happens if you plant a tree too deeply?

When a tree is planted too deeply, it’s likely to develop fungal or bacterial diseases, succumb to insect pests, and eventually die. Common problems seen in trees planted too deeply include:

  • Rotting – Trees planted too deeply can suffer extensive rot at the base of the trunk.
  • Foliage problems – Deep planting causes dwarfed leaf size, defoliation, and leaf yellowing.
  • Reduced growth and dieback – Trees planted too deeply often have branch dieback, splitting bark, and overall reduced growth rate.
  • Frequent pest infestations and destructive diseases – Pests such as emerald ash borers are more likely to attack a tree when it is weak, as are any number of bacterial and fungal diseases.

If you see any of these signs or symptoms of tree distress, take a look at the base of the tree. If you can’t see the trunk flare, the problems are probably due to deep planting.

Symptoms of tree decline might not show immediately, but can be building for years after burying a tree’s root collar. Without fixing the underlying problem, the tree will continue to decline and will eventually die.

This tree was planted without removing it from the burlap beforehand. Always remove a tree from the container or burlap before planting it in the ground.

This tree was planted without removing it from the burlap beforehand. Always remove a tree from the container or burlap before planting it in the ground.

How to Find the Root Flare on a Sapling

Carefully examine the root ball before digging a hole for planting. You’re looking for the spot where the trunk widens out into the root structure. This widening area, or root flare, will develop into strong buttress roots to help support the tree. But to do that, it must be above (or just at) the level of the surrounding soil.

Unfortunately, most new trees are buried too deep in their container or burlapped rootball. Don’t make the mistake of assuming that your tree should be planted at the same depth as you found it in the container or burlap!

If the tree is in a container, carefully pull the container off. If balled-and-burlapped, pull back the top coverings. Then start gently brushing soil away from around the tree trunk until you find the root flare. It could be as much as 6 inches down.

A properly planted tree with trunk flare visible.

The trunk flare (or root flare) is visible on this newly planted tree. The mulch is not piled up like a volcano, nor is the mulch touching the tree trunk.

How Deep to Plant the Root Ball

Once you find the root flare, you’ll know how deep to plant the root ball. That’s when you can start digging the planting hole.

CALL BEFORE YOU DIG (CBYD). Prior to doing any digging, even if only with a shovel, be certain that there are no wires or pipes underground that you might hit. CBYD is a free service that provides this information. Call them at 811. This is a critical first step in tree planting.

Dig a planting hole only deep enough to ensure that the root flare will stay exposed just above the soil line. Remember that the tree will settle in and lower a bit after planting, so higher is better.

>> See our complete tree planting tips

If soil is poorly drained, which is often the case with clay soils, it’s best to plant the root ball a bit higher to encourage drainage.

While planting too deep is a concern, planting overly high is also a problem. If the root system is barely buried, the tree is very likely to topple over. Plus, it won’t be able to absorb the moisture and nutrients it needs from the surrounding soil.

Still, if in doubt about the correct planting depth, it’s better to plant too high than too deep.

A conifer tree planted too deeply.

This conifer tree was planted too deeply.

Avoid Mulch Volcanoes!

After planting, we recommend spreading a layer of mulch around the tree to protect it, prevent weed growth, conserve moisture, and more. However, using mulch isn’t a case of “if some is good, more is better.”

While proper mulching is very beneficial for a tree, piling mulch high around the root flare is extremely damaging. Do not use so much mulch that the tree looks as if it has a “mulch volcano” at the base of the trunk!

A mulch volcano creates the same tree problems as burying the root flare with soil. Plus, it creates a moist environment that’s perfect for fungus and other pathogens to flourish and attack the tree. We often see tree trunks completely rotted out under the mulch.

Mulch piled around tree trunks also:

  • attracts rodents and other bark-chewing pests that girdle and kill the tree,
  • can “bake” (and kill) tender tree bark as it heats up and decomposes, and
  • can compact to the point that water cannot penetrate it to reach the tree roots below.

Mulch should absolutely not touch the tree trunk; mulch volcanoes are a death sentence for trees.

PRO TIP:A general anti-volcano rule of thumb for newly-planted trees is the 3x3x3 rule: mulch 3 inches high, 3 inches from the trunk, with a 3-foot-wide circle around the tree.

A Rayzor's Edge employee evaluates a tree, checking for decay before the roots are exposed using an air spade.

A Rayzor’s Edge employee evaluates a tree, checking for decay before the roots are exposed using an air spade.

What To Do If The Tree Was Planted Too Deep

If you have a tree that is clearly planted too deep, call the arborists at Rayzor’s Edge to evaluate the tree. Depending on where the tree is located and its overall health, we may be able to save it with a process called air spading.

Air spading a tree is done to uncover the root flare collar and top root structure. The process is simple; instead of digging (which could damage tree roots), an air spade blasts the soil away with high-pressure air. It’s a messy procedure but much safer for the tree. And don’t worry, we put up barriers to protect nearby objects from flying dirt!

With the trunk flare and roots exposed, we can examine the flare for decay and correct any root problems. If the base of the tree is structurally sound, we’ll then backfill the excavated area with soil to the proper depth.

Unfortunately, when we discover decay or serious root problems, tree removal may be your only option. If the tree’s root flare has been buried for too long, it may not be possible to save the tree.

A conifer tree with roots exposed after air spading

After Rayzor’s Edge used an air spade to expose the root zone, you can see how the roots of this conifer tree were tangled and growing at the surface.

Not Sure How Deep to Plant Your Tree?

Feeling confused or need help to better determine planting depth? Why not plant it the right way from the beginning! Contact Rayzor’s Edge and our team will come out to help you install the tree correctly. Our certified arborists and experienced teams can help your trees stay healthy and well-adjusted as they mature.

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