Examples of lion tail pruning can be seen throughout the Phoenix area. In this picture, the tree in the foreground— as well as several behind it—have been severely pruned, resulting in poorly shaped, unhealthy landscape trees.

DESERT GARDENING 101

So-called “lion tail” pruning of mature trees is a common—but misguided—practice in the Phoenix area. It often is performed by members of maintenance crews who believe they are preventing storm damage by “thinning” the tree. In fact, this drastic pruning harms a tree’s health and produces potential hazards.

Lion tail pruning is easily recognized. The method strips all lateral branches and foliage from the interior of a main branch, leaving a clump of foliage at the branch tip that resembles a lion’s tail tuft.

Problems created by this type of pruning include the following:

• Bare bark tissue on stripped branches becomes susceptible to sunburn. Sunburned bark cracks, which weakens the branch and creates openings for pests and bacterial or fungal diseases.

• End-heavy branches whip about in windstorms and break easily.

• Stripped foliage reduces the tree’s ability to photosynthesize and create food for continued growth.

• The dramatic loss of foliage sends the tree into stress, often triggering the release of chemical signals that attract insect pests such as bark beetles.

• After overpruning, the tree is genetically programmed to respond to “starvation” by pushing forth lots of crowded, weakly attached growth (commonly called watersprouts) in the tree’s interior. This growth is not well-anchored within the tissue of the parent branch, and as the sprouts become thicker and heavier, they are prone to snap off.

HIRE AN EXPERT
A tree trimmer who practices lion tail pruning causes more damage than the service is worth. In fact, if a tree has been properly pruned, branches and foliage remain well-spaced throughout the canopy, and the work is barely noticeable. Never remove more than 25 percent of a tree’s foliage, branches and shoots in a year, advises Cathy Rymer, Certified Arborist, and water conservation coordinator for the city of Chandler.

“Trees that are overpruned require more water and nutrients as they struggle to replace the foliage that has been lost,” Rymer explains. “In addition, the soil under the tree canopy is now exposed to additional sunlight, increasing the loss of moisture to evaporation. Tender feeder roots located just under the soil surface become vulnerable to increased temperatures as the sun heats the previously shaded soil.”

If you have a mature tree with a large canopy and are worried about safety issues, contact several certified arborists. As with any business, prices quoted will vary, so it is always good to get several bids. Hiring maintenance workers just because they offer to do a job inexpensively is not advisable. It is best to first check whether they have had proper training.

The University of Arizona Cooperative Extension offers advice on How to Hire a Tree Expert at ag.arizona.edu/pubs/garden/az1003.pdf.