Douglas L. Airhart & Guy Zimmerman III

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Transplanting Landscape Trees- Planting Depth:

Planting depth is probably the most common error made when transplanting trees. Our experiences and observations indicate that trees are frequently planted too deeply into the ground.

Detailed Transplanting of a small tree. Video Vignette (See it live!)

(Figure 4-1) Trunk Flare Not Visible

If you cannot see the trunk flare at purchase, excavate the top of the ball to expose it. This tree had been planted too deeply at the nursery. The root mass is distinctly restricted and the trunk is subject to disease and decay.

Illustration from Principles and Practice of Planting Trees and Shrubs, copyright International Society of Arboriculture. Used with permission.

This may occur at the nursery during planting or the soil may build up because of cultivation practices. In this case the trunk flare will not be visible at the surface of the root mass.

(Figure 4-1a) Trunk Flare Not Visible:

The trunk flare of this tree was not visible.

(Figure 4-1b) Girdling Root:

The initial excavation identified at least one major girdling root. Further investigation revealed many more girdling roots below this one. Unfortunately, this is typical for maple trees that have been planted too deep.

(Figure 4-2) Excavated Trunk Suckers.

Suckers had emerged from the rootstock tissue that was below grade at the nursery. Note boundary of planting hole still visible after two years.

Used with permission of Tennessee Tech University, (Photo courtesy of J. Plant, 2002).

Be sure to excavate the soil to find the trunk flare before transplanting otherwise the buried trunk may develop suckers. This concern holds true for containerized trees as well.

If a tree has been planted too deeply you may be able to see space around the trunk where it has ‘wiggled’ in the breeze. Remove the upper portion of the potting mix until the trunk flare is exposed.

(Figure 4-3a) Planted Too Deep.

The trunk is "wiggling" a hole in the backfill soil. Excavate down to the trunk flare and re transplant to a shallower, proper depth.

A visible trunk flare is the proper level for the transplant depth.

(Figure 4-3b) Replanted.

Trunk flare is visible after repositioning the tree.

(Figure 4-3c) Trunk Flare Planted Too Deep:

The trunk flare of this freshly planted tree was not visible. A simple excavation revealed the trunk flare about four inches below the surface. The dip in the rope makes the depth apparent.

(Figure 4-3d) Possible Solution for Trunk Flare Planted Too Deep:

Coarse river stone is used to fill the excavated basin. The stone allows for trunk expansion and for air to circulate around the trunk.

Good Planting Techniques:

Three relatively new guideline are suggested for planting trees:

1. The hole should be NO DEEPER THAN the root ball,

2. The hole should be three to four times WIDER than the root ball, and

3. Mulch should cover the ENTIRE planting hole, but NOT be piled onto the trunk of the tree.

Contrary to popular belief, the burlap material should be removed because it may not dissolve below ground. The best suggestion is to remove all of the burlap. But at the least the top third of the burlap should be cut off to allow new roots to grow unobstructed. The biggest difference from previous planting diagrams is the hole itself, that has the shape of a shallow basin.

(Figure 4-4) Proper Planting Depth.

The hole is only as deep as the root ball, and is two to three times wider.

Note that the burlap and wire are removed about half way down.

	The hole is only as deep as the root ball. This provides a firm base that will keep the tree from settling to submerge the trunk flare.
	The hole is 3 to 4 times wider than the root mass. This prepares a loosened and aerated soil in the area that the new roots will grow.
	A small water retaining berm is placed at the edge of the hole to help hold irrigation water in the root zone.
	The mulch is applied over the entire transplanting hole. This will help retain moisture in the root zone and possibly protect the trunk from mower damage. The mulch is applied neither onto the trunk flare nor up onto the trunk. Mulch on the trunk can allow the bark to decay and make the tree likely to become diseased or rot through.
	Staking is not usually needed on small trees. If you believe stakes are needed, the stakes are placed well outside the existing root mass, and the holding straps are fastened loosely to the trunk to let it partially sway in the wind as it would naturally. This will let the roots develop strength needed to support the weight of the tree against wind throw.

(See Mulching & Staking for more detail on these subjects).

Example: Young Red Maple- Video Vignette (see it live!)

As we were walking by this recently planted red maple, we could not see the trunk flare. It took just a short period of time to excavate the soil with a hand trowel to expose the trunk flare, which was about four inches below soil grade. Apparently the tree had been planted using a backhoe to dig the hole, and the tree was planted too deeply. Use the handle of a shovel or a piece of lumber to span the hole and determine the soil grade. The trunk flare should not be below this grade when transplanting is completed.

Please refer to Figure 3-2c (scroll about half way down the page) to see this tree and the excavated trunk flare four years later.

Example: Mature Red Maple- Video Vignette (see it live!)

This maple did not have a visible trunk flare. We began to excavate the soil and immediately found two large girdling roots restricting the trunk growth. We used hammer and chisel to cut away the girdling roots and then continued our excavation, only to find more girdling roots at deeper levels. By the time we were ten inches deep, we still had not found the root flare. But the trunk was so narrow at that depth that we determined the tree to be a hazard because it was adjacent to a sidewalk on the main quad of a university. The tree was removed immediately.

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TLCforTrees.info is maintained by: Douglas Airhart, Ph.D. Certified Arborist & Jeff Plant, Ph.D, Last Updated on: 07/11/03