Bill Pramuk
Trees & People

About 15 years ago I was asked to evaluate the condition of an old valley oak that was showing signs of decline a few years after a water main trench was dug through its root zone. Its canopy of foliage was very sparse that summer and some of the branches were dead.

I was convinced it was dying. Fortunately, another arborist was of the opinion that the tree could be saved and the owners were willing to give the tree some special care and time to recover. With pleasure, and a twinge of embarrassment, I watched the tree gradually regain vitality over a period of about 10 years. It is still standing today in apparently good health, a testament to the recuperative power of trees, the value of patience and the difficulty of knowing when a tree is beyond saving.

In contrast, I recently witnessed the decline of a large Douglas fir tree that had sustained severe damage to its root system. I was asked if the tree was still alive and whether or not it could be saved. In this instance, considering the severity of the damage and how I’ve seen other Douglas firs decline, there was no doubt that the tree was dying. When I mentioned the tree to another arborist, his response was  “Oh yeah. I’ve been watching that tree die for some time now. I was wondering when they would take it down”.

A third example is an olive tree, one of these big, transplanted specimen olive trees that are so popular now around Napa Valley. It  was one in a group of four trees. Three were doing fairly well in the first year after transplanting. They really aren’t expected to grow vigorously for several years. (“First they sleep, then they creep, then they leap.”) But they should not drop all of their leaves, which is what the fourth tree was doing.

Having seen this before, I knew that :

1. Olives are about the toughest survivors imaginable. 

2. If there is green cortex — the tissue just under the paper thin layer of outer bark — the branch is not dead yet.

3. With proper drainage and carefully scheduled irrigation, olives usually have a fighting chance.

I told the owners all of this and suggested they wait through the following summer, if they were willing to live with a dead looking tree for a while and follow through on the monitoring and irrigation management. They gave it some time, but when there were no signs of life through August, they decided to pull the tree. Then, as the removal was being scheduled, the tree began to sprout new shoots, even from some of the smaller branches. So, they decided to save it. If all goes well, that tree could remain for centuries with its three companions.

Making the decision whether to try and  save or to remove a sick tree can be difficult and complicated. A relatively simple protocol will help to sort out priorities.

Tree risks

A dying or decaying tree (or any tree for that matter) may present a hazard if three components are present: 

1. A tree with a potential to fail 

2. An environment that may contribute to that failure 

3. A person or object that would be injured or damaged, i.e. the target. (“Evaluation of Hazard Trees in Urban Areas,” Matheny and Clark, 1991).

So, the tree in question must be assessed for risk. Olives, which are relatively short and have very tough wood, present a small potential to fail in a way that would cause harm. In contrast, a huge old oak with extreme decay in the trunk, situated in a wet, irrigated landscape with limbs over a roof  would have all of the components comprising a hazard.

Tree species and environment

Tree species have inherent differences in their ability to generate new roots and shoots. That ability is influenced by the life history of the individual tree and the surrounding environment. In some cases, declining trees can be revived by helpful changes in the environment such as mulch, careful irrigation, special soil treatments and so forth, but the species and the individual specimen must be considered.

For example, Douglas fir trees cannot generated new shoots from the trunks or branch stubs; only from live buds. In contrast, coast redwoods can sprout from latent buds almost anywhere on the tree. A Doug fir declining because of damaging changes in environment has inherently less potential to recover, even if the environment is improved.

Owners’ prerogative

After the experts have had their say, the responsibility for the final decision falls to the owner. As it says, in part, in my ‘Arborist Disclosure Statement’:

“... Clients may choose to accept or disregard recommendations or to seek additional advice from others... remedial treatments ... cannot be guaranteed.”

Bill Pramuk is a registered consulting arborist. Visit his Web site, www.billpramuk.com, e-mail questions to info@billpramuk.com, or call him at 226-2884.