Good tree pruning something of an art form

The Collier County Land Development Code, Ordinance No. 91-102, is armed with teeth and with sound knowledge from arboricultural experts within the industry and university systems. Look for someone that is a certified arborist when you have some serious tree pruning to do (see www.isa-arbor.com/findArborist/findarborist.asp).

Also, for tree pruning, one must have one of the following county occupational licenses, either a Landscaping Contractor or the Tree Removal and Trimming Contractor. Call the Collier County Contractors' Licensing Division (403-2431) to confirm if a company has the appropriate license. Companies that only have a Lawn Maintenance occupational license cannot prune trees.

Hat-racking is stubbing a branch, a willy-nilly cutting of branches, far from a bud or a new leader. For a plant to "heal" or compartmentalize the pruning wound, the cut needs to be made at a point where the plant tissue can grow over or engulf the injury. This is not possible when dealing with, essentially, a broken-off twig. The plant tissue is not able to grow over the stub.

It may attempt to grow over the cut stub (see accompanying picture) and result in a weak flap that will break out easily. Or it may result in a domino affect, that is, the cut end will decay, which progresses to internal twig rot, which will lead to trunk rot, which will result in an unstable or sickly tree that will be unsightly.

Poorly placed cuts will also lead to competing laterals sprouting into an unnatural-looking witch's-broom appearance. There should be one dominant leader (one main trunk), depending on the species.

Professional arborists, as well as our code enforcement personnel, abide by the American National Standard, ANSI A300-2001 "Standard Practices for Trees and Other Woody Plant Maintenance" guidelines (see the Florida chapter's Web site to order the standards for $20: www.floridaisa.org).

Some ANSI pruning standard practices are:

-- "Not more than one-fourth of the foliage on a mature tree should be removed within a growing season." Note: I suspect that this is not as critical in southwest Florida with the longer growing season. See section 5.5.3.

-- "When a branch is cut back to a lateral, not more than one-fourth of its leaf surface should be removed. The remaining lateral should be large enough to assume apical dominance." In other words, a large leader will suppress (a hormonal thing) excessive sprouting.

-- "Thinning should result in an even distribution of branches on individual limbs and throughout the crown." Ignoring this concept leads to over-lifting and "lion's-tailing." Lion's-tailing puts the weight load on the ends of the branches, making branches more prone to break-outs in high winds.

Code enforcement will take into account the species of tree, the site limitations (parking or building clearance) and other extenuating circumstances in deciding if an infraction has occurred. A tree that has been neglected for many years may require several years of pruning to reshape it and some drastic cuts may be required.

For example, live oaks have multiple leaders and crossing branches and, like many of us in our youth, just can't seem to find the straight path and may require a lot of pruning over an extended period of years to develop properly. It is better to train them up right when they are young in order to avoid the severe pruning consequences later. The spirit of the ordinance is to protect the quantity and quality of our urban and rural forests.

Good pruning is also something of an art, as with a good haircut, the end result will be subtle and perhaps even go unnoticed at first glance. The finished job should not scream out at you.

For more information/literature contact the extension office. Also contact the Collier County Code Enforcement (403-2413) for code literature or enforcement details.

An excellent web site is: hort.ifas.ufl.edu/woody/pruning. Also see Pruning Landscape Trees and Shrubs, Circular 853, at: edis.ifas.ufl.edu/MG087.

Doug Caldwell is a certified arborist and the commercial horticulture extension agent with the University of Florida Collier County Extension Service. E-mail dlcaldwell@mail.ifas.ufl.edu ; call 353-4244.