Pruning Landscape Trees, Environmental Hort. Dept. UF/IFAS

From Landscape Plants Website
by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida

Pruning Landscape Trees

When to Prune ¹

The best time to prune live branches may depend on the desired results. Growth is maximized and defects are easier to see on deciduous trees if live-branch pruning is done just before growth resumes in early spring. Pruning when trees are dormant can minimize the risk of pest problems associated with wounding and allows trees to take advantage of the full growing season to begin closing and compartmentalizing wounds.

Removal of dying, diseased, broken, or dead limbs can be accomplished at any time with little negative effect on the tree. Plant growth can be reduced if live-branch pruning takes place during or soon after the initial growth flush. This is when trees have just expended a great deal of stored energy to produce roots, foliage, and early shoot growth so pruning at this time is usually not recommended due to the potential stresses. Stressed trees should not be pruned at this time.

Flowering can be prevented or enhanced by pruning at the appropriate time of the year. To retain the most flowers on landscape trees that bloom on current season’s growth, such as crape-myrtle (Lagerstroemia spp.) or linden (Tilia spp.), these trees are pruned in winter, prior to leaf emergence, or in the summer just after bloom. Plants that bloom on last season’s wood, such as Prunus, should be pruned just after bloom in order to preserve the flower display. Fruit trees can be pruned during the dormant season to enhance structure and distribute fruiting wood, and they are pruned after bloom to thin fruit.

Pruning Cuts

Fig. 1 Branch union examples

Here are several examples of removing branches from trunks or removing small branches from larger branches. Always cut just outside the branch collar.

There are Four Different Pruning Cut Types
1. Removal cut: large removal cut, do not make flush cuts
2. Reduction cut
3. Heading cut
4. Removing dead branches

1. Removal Cut


Fig. 2 Visible collar	Fig. 3 No visible collar	Fig. 4 No collar and included bark

There are three possible situations trees present to you when removing branches.
Fig. 2. Cut to the edge of the collar when one is visible
Fig. 3. If there is no visible collar, begin where the top of the branch makes an abrupt turn toward the trunk and cut outside an imaginary line drawn parallel to the trunk
Fig. 4. Make the final pruning cut at the base of the actual connection between the branch and trunk when there is included bark in the union

There is no need to apply paints, wound dressings, or chemical formulations of any type to the surface of the cut.


Fig. 5 A good removal cut	Fig. 6 A poor removal cut

The correct way to remove a branch from the trunk is to cut just outside the edge of the swollen branch collar.
Fig. 5. Cutting through the collar (right) removes an important decay defense mechanism called the branch protection zone. This zone is located inside the collar. This type of cut has been called a removal cut because it removes a branch from the trunk
Fig. 6. A poor removal cut called a flush cut removes the branch bark ridge and results in exposure of a thicker bark section above the cut than the sides and underneath


Fig. 7 Before removing a branch	Fig. 8 After removing a branch

Fig. 7. Cut along the "yes" line to remove the branch on the right. This cuts just outside the branch collar. Cutting through the "no" line cuts through the collar and removes the branch protection zone
Fig. 8. Removing the branch appropriately leaves the collar intact


Fig. 9 Good pruning cut	Fig. 10 Flush cuts are not good for trees	Fig. 11 Several months after flush cut	Fig. 12 Good pruning cuts

Fig. 9. Good pruning cuts leave the branch bark ridge and the collar intact and on the trunk. Note the ridges that remain on the three cuts in this photo.
Fig. 10. The cut in the center of the photo removed the collar and the branch bark ridge. This is referred to as a flush cut. The cut on the bottom was appropriate and left the collar and branch bark ridge intact.
Fig. 11. Callus typically begins to form on the sides of a flush cut before it forms on the top and bottom. The branch bark ridge is missing on top of the cut. This is a good way to determine when flush cuts are made.
Fig. 12. Good cuts are typically round in cross section as shown above. Note the branch bark ridge is intact on the sides and top of each union.

2. Reduction Cut
A reduction cut (also referred to as a drop-crotch cut) shortens a branch by removing a stem back to a lateral branch that is large enough to resist extensive dysfunction and decay behind the cut. This is generally interpreted as cutting back to a lateral branch that is at least one-third the diameter of the cut stem. Sprouts commonly follow a reduction cut. In most cases these should not be removed because they help the retained portion of the branch retard decay. When the branch that remains is less than about one-third the diameter of the cut stem, the cut is considered a heading cut. Heading cuts are not considered appropriate in most instances in the landscape. Heading cuts are sometimes necessary when attempting to restore trees following storm damage.


Fig. 13 A reduction cut removes a stem back to a lateral branch.	Fig. 14 Large reduction cut	Fig. 15 Small reduction cut	Fig. 16 Reduction cuts in the canopy

Fig. 13. A reduction cut removes the stem back to a living lateral branch that is large enough to assume the terminal role of the removed portion. This typically is interpreted in the profession as about 1/3 to 1/2 the size of the removed portion.
Fig. 14. The reduction cut is very useful for structural pruning techniques. A reduction cut slows growth on the cut stem or branch. There is one reduction cut in the photo above in the upper part of the large right-hand stem. This will slow the growth of the right hand stem and push more growth into the larger stem on the left.
Fig. 15. Reduction cuts are useful for developing a dominant leader in the canopy of shade trees. Reduction cut can be seen on the top left stem. This cut slows growth on that stem which subordinates it to the central leader.

3. Heading Cut
Fig. 17. A heading cut is a type of pruning cut that prunes a shoot no more than 2 years old back to a bud; cutting through an older stem back to a lateral branch less than 1/3 the diameter of the cut stem; or cutting a stem to an indiscriminate length. Heading cuts on trees typically are not appropriate in the landscape unless trees are being restored following a storm.

Fig. 17
Heading cut

4. Removing Dead Branches
To remove the dead stub cut to the place where the live tissue begins. The slight swelling on the branch base about an inch out from the trunk represents the beginning of live tissue.


Fig. 18	Fig. 19

Fig. 18. To remove the dead stub cut to the place where the live tissue begins.
Fig. 19. The slight swelling on the branch base about an inch out from the trunk represents the beginning of live tissue.

Photo Examples of Pruning^{ext. link}

ROOT PRUNING TREES ²

Fig. 20

Root pruning landscape or nursery trees can take many forms. Techniques vary depending on objectives and tree age. Nurseries routinely root pruned certain species to create dense root systems. Landscape managers root prune to reset sidewalks and curbs, and to reduce conflicts with other structures. Contractors root prune to prepare for building and utility installation. Arborists root prune, under certain circumstances, to improve tree life span.

Root pruning guidelines for landscape trees:
1) Container production practices: roots
2) Root pruning at planting
3) Removing (pruning) stem girdling roots

1. Container production practices: roots
Roots in containers grow quickly to the container wall, sometimes in a matter of days or weeks. These sometimes branch, but often deflect without branching to circle around the container wall and/or descend down the container wall. Occasionally roots grow up the container sides. These root defects are the biggest challenge to growing trees in containers because these can lead to tree health and stability problems. There are many methods of producing trees in containers, and there are many container types designed to reduce defects. Combined with root pruning each time the plant is potted into a larger container, quality trees can be produced in many container types.

2. Root pruning at planting
New research (2009) is suggesting that slicing root balls does not result in more roots in landscape soil nor improve tree stability in the landscape. Instead we think that the entire outer inch of the sides and bottom of the root ball should be removed.

Conventional wisdom has been to slice the sides of the container root ball as deeply as possible to sever circling roots. Also cut kinked and circling roots that occur on the top of the container (see photos below). This will reduce likelihood of the tree dying from these severe root defects later. In most cases there is little or no negative impact on the tree from this aggressive root cutting, as long as trees are irrigated. The positives far outweigh the negatives. Remove roots that are positioned on top of the main flare roots as shown below.

Fig. 21
Expose the roots by removing soil or media
from the top of the root ball. All these circling
and crossing roots should be removed.

Fig. 22
Begin removing roots that circle and cross the
top of the root ball.

Fig. 23
When completed the main flare roots will be
visible as shown above. The pink line was at
the original soil level.

Fig. 24
These roots should be removed because they
are likely to strangle the trunk.

Fig. 25
After removing the stem girdling roots the tree
has a much better chance of thriving in the
landscape.

3. Removing (pruning) stem girdling roots
Roots that are not directed away from the trunk can cause health issues for the tree, and tree death in certain cases. Look for roots that are circling close to the trunk, roots that are embedded in the trunk, or those that are crossed over main roots at the base of the trunk. Roots circling or touching the trunk are often referred to as stem girdling roots. These can reduce the flow of water, nutrients, and sugars at this point on the trunk. On some species of trees, stem girdling roots cause death to the bark above the root.

Treatment: If these are less than about one-third the trunk diameter, and they can be removed without damaging the trunk, then carefully cut and remove them (see photos below). This will allow roots and trunk under the girdling root to develop properly. Some arborists have removed larger girdling roots with no adverse affects on the tree. Trees often respond to removing girdling roots with increased vigor.

Fig. 26
This shows a stem girdling root growing in
mulch placed on the trunk at planting. Keep
mulch pulled back about 12 - 18 inches from
the trunk to prevent this. Note the trunk injury
(extreme left on trunk) caused by the girdling root.

Fig. 26
After removing the stem girdling root, the root
system and trunk below this point can expand
normally. Notice the indentation in the trunk
where the root was removed. The root
wrapping the trunk restricted the trunk from
expanding at this point. It is easy to see why
these are not good for trees.

Fig. 28
This stem girdling root was visible at the
surface without removing soil or mulch.
Carefully cut the root at the point where it
emerges from the trunk and remove as much
of it as possible without damaging the trunk
and other roots.

Further Reading
Tree Structure Index^{ext. link}
Tree Pruning Cue Cards
Pruning at Planting^pdf
Pruning Young Trees ^pdf
Pruning Established Trees^pdf

Tree Pruning Programs
Young Trees^pdf
Mature Trees^pdf
A Plan for Training Shade Trees^pdf
Assessing Hurricane Damaged Trees ^pdf
Restoring Trees after a Hurricane^pdf

Back to
Pruning and Training Page

Bibliography

¹ Gilman, Edward F. "Pruning Shade Trees in the Landscape." Environmental Hort. Dept., UF/IFAS, Last modified 22 May 2014, Landscape Plants, hort.ufl.edu/woody/pruning.shtml. Accessed 30 May 2014.
² Gilman, Edward F. "Root Pruning Trees." Environmental Hort. Dept., UF/IFAS, Last modified 24 Jan. 2020, Landscape Plants, hort.ufl.edu/woody/root-prune-summary.shtml. Accessed 22 Mar. 2021.

Photographs

Fig. ¹ Gilman, Edward F. "Pruning cut types: Live branch removal." Pruning Shade Trees in the Landscape, Environmental Hort. Dept., UF/IFAS, ENH847, Landscape Plants, hort.ifas.ufl.edu/woody/documents/cuttypes.pdf. Accessed 30 May 2014.
Fig. ^{2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19} Gilman, Edward F. "Pruning Shade Trees in the Landscape." Environmental Hort. Dept., UF/IFAS, Last modified 22 May 2014, Landscape Plants, hort.ufl.edu/woody/pruning.shtml. Accessed 30 May 2014.
Fig. ^{20,21,22,23,24,25,26,27,28} Gilman, Edward F. "Root Pruning Trees." Environmental Hort. Dept., UF/IFAS, Last modified 24 Jan. 2020, Landscape Plants, hort.ufl.edu/woody/root-prune-summary.shtml. Accessed 22 Mar. 2021.

Published 30 May 2014 LR. Last update 22 Mar. 2021 LR