For:
By: Daniel E. Mullins
Extension Horticulture Agent
Big,
I have been busy making photographs and documenting all of the different ways that Hurricane Ivan damaged our local trees, and it has been quite an experience. I thought at first that this could be done over a short period of time, but the different ways and degrees of damage have resulted in a long list that continues to expand.
Of all the tree damage that has been seen, the trunk splitting of some of our largest live oaks has stirred the most emotion. Some of these giants, with trunk diameters of four feet or more, were split vertically down the middle.
Every case that I have seen is virtually identical. Trunk splitting happened to trees that were forked within a few feet of the ground and had two or three co-dominant leaders. At the junction of these large branches the angle of growth was narrow, allowing bark to form between each. So, instead of a wood to wood attachment where they touched, there is only bark touching bark except near the bases.
Close examination of a split tree reveals that instead of a solid trunk, it was actually forked at or near ground level. As it grew, bark grew between these multiple trunks instead of wood. This condition is described as having “bark inclusion,” or bark that was trapped between two or more limbs.
As the tree grows, it tends to grow outward due to competition from other branches. This adds tremendous weight over time. Live oak wood is said to weigh over eighty pounds per cubic foot. This downward pressure places stress on a rather limited, weak attachment at the base.
Most of our big old live oaks were able to tolerate normal weather conditions, but not the winds of Ivan. The violent bending, shaking and twisting was more than these bark included branches could tolerate. As a result, they either split apart, or long vertical cracks remain in some.
Residents are advised to examine their large live oak trunks in order to determine if splitting or cracking has occurred. If it has, then consider these to be hazardous or dangerous trees that are subject to falling.
Especially valuable or historic trees that still stand but have trunk cracks or splits are sometimes preserved by cabling or bracing. This is a highly specialized practice that involves drilling through the center of branches at selected locations and installing special heavy duty rods for bracing or bolts for cabling.
I hasten to add that this should be done only in the case of a very valuable tree. It involves the hiring of a highly trained and experienced professional that specializes in this practice.
Note: There is no short cut to proper bracing or cabling. Do not attempt to hold the tree together by wrapping cable, chain or straps around the trunk or branches. Such a practice can result in the girdling of the branches, and in most cases would not provide strong enough support.
Question of the Week: My azaleas and other shrubs survived the storm, but are leaning due to the high winds. Should they be straightened up? If so, what is the procedure?
Answer: Don’t attempt to straighten shrubs at this late date unless they are leaning severely. Many have already begun re-growth and are attempting to fill in the downwind side and become symmetrical once more. Though the main stem will remain at an angle, most shrubs will regain their previous shape.
Digging around, and returning these
plants to a vertical position would waste the energy that they have expended
over the past two months. Though not a
perfect solution, it’s better than the double shock that would result.