Spontaneous Limb Failure Is Real

90605thumbIt sounds like science fiction, but it is not. Every spring and during particular summer weather, limbs can fall from trees without warning, and seemingly for no reason at all. It happens when least expected, while the weather is warm and perhaps humid, but notably without wind. The lack of wind is what makes it so unexpected. It is a phenomenon known simply as spontaneous limb failure.

Those who witness it might think that the arborists they call to clean up the mess will not believe their descriptions of what happened. Yet, arborists are familiar with it. Quite a few species of trees are notorious for it, especially in urban landscapes where they get watered regularly. Most of such trees are either chaparral trees that do not expect much water, or riparian trees that do expect it.

Spontaneous limb failure occurs as warmth accelerates vascular activity, but humidity inhibits evapotranspiration, which is evaporation from the foliage. Accelerated vascular activity increases the weight of the foliage. Inhibition of evapotranspiration limits the ability of the foliage to eliminate some of the excess weight. Limbs break if unable to support the increasing weight of the foliage.

Spontaneous limb failure is not as easy to predict as the more familiar sort of limb failure that is caused by wind. Limbs that get blown down typically exhibit some sort of structural deficiency or disfigurement prior to failure. Some limbs that succumb to spontaneous limb failure do so as well, but most do not. They just happen to be the healthiest and most densely foliated parts of a tree.

Native coast live oak and valley oak are the two most familiar of the chaparral trees that are notorious for spontaneous limb failure. Native cottonwood, willow, box elder and sycamore are riparian trees that are perhaps even more susceptible to spontaneous limb failure. Sweetgum, carob, stone pine and various eucalypti are some of the exotic trees that might drop limbs spontaneously.

In summer, spontaneous limb failure is less likely as growth slows and limbs strengthen.


The Davey Tree

P90317This is no common Douglas fir. It is the ‘Davey Tree’, named after the tree service that so diligently prunes it for clearance from the utility cables above. Yes, I can see as easily as you can how disfigured it is. The plan is to cut it down before it falls apart. At least that is the excuse for cutting it down. It is relatively short an stout, so is likely quite able to support its own weight, regardless of this disfigurement. We really just want it gone because it is so unsightly.
Most who see the Davey Tree are quick to blame the disfigurement on those who prune it for clearance. They do not consider that without such pruning, the utility cables would eventually be ruined and unable to deliver the electricity that so many of us use. Those who prune the trees do what they must to keep the electricity and other utility cables operational. Unfortunately, such work sometimes ruins trees.
As an arborist who sometimes works with other arborists who must perform clearance pruning, I am more likely to blame other landscape professionals. Some landscape designers design landscapes with trees that get too tall or broad within utility easements. Heck, many designers do not even designate where such easements are on the drafts of their landscape plans. Some so-called ‘gardeners’ plant such trees in utility easements with no plan at all. For what they all charge for their services, landscape professionals should know better than to put inappropriate trees into situations where they will eventually need to be mutilated or removed. Not many think that far ahead, or even care.
Anyway, the inappropriate location and disfigurement of the Davey Tree really can not be blamed on anyone. It is a wild tree that grew there from seed.P90317+

Horridculture – Cruel and Unusual Punishment

P90213This landscape is nothing fancy. It is out in front of a fast food establishment on Ocean Street in Santa Cruz. It is low maintenance, and starkly simple. It would be nice if the so-called ‘gardeners’ would cut back the African iris and English lavender a bit better, but they may have left them like this so that they are less likely to get trampled. The colored chips get replenished regularly, and the trash gets harvested quite efficiently. As I said, it is nothing fancy. The only remarkable feature had been this exemplary crape myrtle in the middle.
Only a few weeks ago, it was a perfect small specimen. Even though it is still quite dinky, the main stems were all at good angles, well spaced and aimed in the right directions. None of the stems were crossing over others, damaged or otherwise misshapen.
I can not explain what happened here since then. Are the so-called ‘gardeners’ trying to make more work for themselves by causing problems that will likely need their attention in the future? Do they just hate their work as much as this abuse implies? Is it possible that someone really believes that ‘this’ is somehow beneficial to the victim?
Each of the two fence stakes is sufficient to support a small tree, if such a tree needs it. If a tree, or in this case, a multi-trunked tree, does not need support, it should not be supported. Otherwise, it becomes reliant on the support. Besides that, these are fence stakes that are designed to be somewhat permanent. Now that they are there, they will probably be there forever. So-called ‘gardeners’ who do this sort of thing are not the sort to remove stakes.
The nylon straps are not flexible to accommodate the expansion of the stems they are tied around. If not removed, they will constrict, or ‘girdle’, the growing stems. What exactly are the straps doing anyway? The two closest to the bottom are tied to one stake, and pass the other to reach the respective stems that they are tied to, rather than tied between each of the two stems and the stake that it is closest to.
Someone certainly put a lot of effort into a whole lot of uselessness that will interfere with the healthy development of this formerly exemplary crape myrtle. Yet, with all this effort, no one bothered to prune it, or even so much as deadhead it. Yes, those are deteriorated floral stems from last summer.P90213+

Greenhouse Envy

P90209KIf there were lawns and fences in this neighborhood, the grass would likely seem to be greener on the other side of the fence. In this situation, the greenhouse probably seemed to be more comfortable than being left out in the storm. This tall Douglas fir tree dropped in to find out. It did not go well. What remains can be seen in the middle of the picture above, just to the right of the fallen fir, and in the close up of the picture below.P90209K+
Miraculously, the two coastal redwood trees that caught and guided the fir to a direct hit on the greenhouse also prevented it from destroying the associated house. Well, at least the redwood on the left did. There would have been less damage if the fir had fallen farther to the right. Regardless, a deck was crushed, an eave was destroyed, but the rear wall of the home was barely nudged. Not even the windows there were broken!
Falling debris punched a few holes in the roof, but without structural damage. The patio of the big building to the right was littered with debris that was easily removed. After limbs are removed from the damaged house, much of the carcass of the fallen fir will remain on the forest floor. It decays efficiently here.
Incidentally, this fir was about to be removed. It had been identified as too risky for the neighborhood. Although they are not visible in the pictures, there are a few other homes in the neighborhood. The cabin that I stayed in for more than a week is just beyond where the top of the fir landed. The stovepipe that is visible in the background of the second of my ‘Six on Saturday – Cabin Fever’ pictures from January 5 is the same stove pipe that is visible on the roof of the home that was nearly destroyed by the fallen fir. https://tonytomeo.com/2019/01/05/six-on-saturday-cabin-fever/P90209K++
(The stove pipe circled by the yellow oval just above the center of the picture above is the same stove pipe circled by the yellow oval just right of the middle of the upper margin of the picture below.)P90209K+++

Six on Saturday: Untimely Death


One of the more unpleasant parts of my work is condemning elderly trees. Redwood and oaks in our region can live for centuries, but none last forever. It is sometimes my job to determine if some of the oldest of oaks have deteriorated to such an extent that they have become unsalvageably dangerous to those around them.

What is worse than that is that there are so many dangerously deteriorated oaks and other trees that collapse before they get removed, and many do so before anyone notices how dangerous they are. Some structural deficiencies and instabilities are concealed to the most thorough of arborists. That is what happened with this big coast live oak, Quercus agrifolia, with a five foot wide trunk, that fell behind Felton Presbyterian Church. I had known for some time that the healthy canopy was heavy and exposed to wind. What I did not know is that the root systems was insufficient to maintain stability when strong wind blew against the healthy canopy while the soil was saturated. The insufficiency of the root system became apparent not only because the tree destabilized, but also because the minimal root system became exposed by the destabilization. There was no evidence of decay or damage within the root system, which are what typically contributes to destabilization.

1. It is amazing that this tree stood for as long as it did with such minimal roots.P90209

2. This is what those minimal roots supported for so long.P90209+

3. Healthy foliar growth on top of the canopy enhanced weight and wind resistance.P90209++

4. Damage was surprisingly minimal.P90209+++

5. This decay within one of the main limbs was a structural deficiency that did not contribute to the destabilization.P90209++++P90209+++++

6. (above) This is the same picture as #5. The red line is at the cross section of where a limb broke or was cut away many years or decades ago. Although the straightness of the zone suggest that it was made by a pruning cut, it is unlikely that the tree was pruned up as high as this section of limb was located, particularly so long ago. As the tree compartmentalized the wound, decay spread inward toward the center from the wound, in a typical pattern that resembles a section of a pie chart, which is marked by the yellow lines. Once it reached the center, decay radiated outward from the center, in a typical circular patter, which is marked by the blue circle. As the center of the trunk rotted and deteriorated, the necrotic zone between it at the original wound continued to rot and deteriorate. By that time this cavity developed, the exterior of the wound had already been compartmentalized by viable wood that did not decay.

This is the link for Six on Saturday, for anyone else who would like to participate:


Horridculture – Disdain For Trees

P90206Okay, we get it; someone really hates trees. That’s fine. Trees are not for everyone. Just cut it down. Put it out of it’s misery. Take away the useless lodgepole stake and strap along with it. Maybe those Canary Island date palms that look like the home of SpongeBob SquarePants in the background will recover from their own form of abuse to compensate for the loss of this seemingly unwanted goldenrain tree.
Apparently, it is not that simple. This goes beyond a dislike of trees, or a mere desire to kill them. This tree seems to have been tortured by someone who enjoys it WAY too much. There were others that were similarly disfigured in this same parking lot in the north of San Jose. They were not pollarded. They were not pruned. There were mutilated, but kept alive for more of the same.
What is worse is that someone was paid for this torture. Property management hired a tree service to ‘prune’ these trees, likely for clearance from lamp poles and parked cars. Was the perpetrator inexperienced, insensitive, or as hateful as the severity of the disfigurement suggests? Well, lets analyze that.
There are plenty of inexperienced people who take jobs in occupations with which they are not familiar. However when the do so, they tend to learn at least the basics about it to avoid doing their work improperly. That obviously did not happen here.
Insensitivity or a lack of concern for the work is possible. However, even someone who does not care about such work is likely to get something about it correct, even if just circumstantially. Well, that did not happen either.
These trees are kept alive because they are more lucrative to the torturer that way. As disfigured as the trees are, they will regenerate new growth that will again need to be pruned for clearance later. Someone who put that much thought into what is being done could have just as easily put forth the effort to do ‘something’ properly in regard to pruning. That is obviously not part of the agenda. The perpetrator really is as disdainful of these trees as the disfigurement indicates.

Arborists Really Know Their Trees

7bd6It is no surprise that there are many different types of physicians within the medical industries. Pediatricians, surgeons, cardiologists, dermatologists, and all sorts of ‘doctors’ are all recognized for their particular medical specialty. Yet, almost all horticultural professionals are known simply as gardeners or landscapers, even though many never work directly in gardens or landscapes.

Production nurserymen grow horticultural commodities (plants). Other nurserymen maintain these commodities while they are marketed. Landscape designers develop the landscapes that many plants inhabit. Only after the involvement of various less familiar horticultural professionals, landscapers install the landscapes, and gardeners maintain them. Somehow, they get too much credit.

Arborists really deserve more credit. They are the physicians of trees, who specialize in arboriculture, which is the horticulture of trees. Much of their work is out of reach to gardeners, and is very distinct from the sort of work that gardeners should be expected to perform. Trees are the most substantial features of a landscape, so really should get the proper attention that they deserve.

The International Society of Arboriculture, or ISA, certifies professional arborists who have passed an examination of their arboricultural expertise, and continue to demonstrate proficiency with discriminating arboricultural standards. Continued involvement with ISA classes, educational seminars and workshops is required to maintain arborist certification. It demands serious dedication.

Besides assessing the health, stability and structural integrity of trees, ISA certified arborists are the most qualified to prescribe any necessary arboricultural procedures, and to direct those who perform these necessary procedures. Most local municipalities require a report from an ISA certified arborist to accompany an application for a permit to remove any protected ‘heritage’ tree.

The website of the ISA, at www.isa-arbor.com, Is an excellent resource for finding certified arborists, and the tree service businesses with which they are affiliated. Arborists can be found by name directly, or regionally by ZIP code or city. The website is also a great resource for information about proper arboriculture and trees, and can help those who are not arborists with selection of trees.

Arborists Are Very Specialized Horticulturists

81205thumbThe first storm of the year has a way of reminding us if our trees need attention. Whether then need to be worked on this year or not, we tend to notice how they blow in the wind, or if they are full of dead and deteriorating debris that falls into the garden or onto the roof. As deciduous trees defoliate, they are less likely to be damaged by wind, but their structural deficiencies become visible.
This is when some of us will contact arborists to inspect and perform necessary arboricultural procedures for trees that have grown to big for us to maintain. We do not want trees to be damaged by the wind. Nor do we want them dropping limbs or falling onto whatever is within their reach. Those that are biggest and most beyond our reach have the most potential to cause major damage.
Arborists are horticulturists who specialize in the horticulture of trees, which is known as arboriculture. They assess the healthy, stability and structural integrity of trees, then prescribe necessary corrective arboricultural procedures, and if necessary, prescribe the best time for such procedures. Most arborists work with a tree service that is equipped to perform the prescribed procedures.
Arborists who are certified by the International Society of Arboriculture, or ISA, have passed an examination of their arboricultural expertise, and maintain their credential by continued involvement with the educational seminars, classes and workshops of the ISA. More information about the ISA, local certified arborists and even arboriculture, can be found at the website http://www.isa-arbor.com.
As mentioned earlier, arboriculture is specialized horticulture of trees. It is not something that gardeners should be expected to perform; particularly mow, blow and go gardeners who are not even proficient with simple gardening. Many arborists can concur that unqualified gardeners sometimes kill trees, and cause much of the damage to trees that arborists must later correct. Besides, arboriculture is the sort of work that can be very dangerous to those who lack training, experience or the necessary equipment.

Trees Hate Cars

P71028That is a myth. They do not hate all cars. They just hate particular cars.
I did an internship with arborists in the summer of 1988, and have never been able to get away from arboriculture. Even as a nurseryman, I still sometimes work for arborists, and inspect trees that they are concerned with. I have seen many of their subject trees that have fallen onto parked cars, homes and whatever trees fall onto. I have noticed particular patterns.
Trees are more careful with Buick, Oldsmobile, Pontiac, Chrysler, Volkswagen, Mercedes Benz, and Datsun or Nissan. I have seen them put considerable effort into avoiding these cars when dropping limbs or falling over. When I was in school in San Luis Obispo, I drove my neighbor’s 1969 Oldsmobile Cutlass out from under his Chinese elm that fell over it. The tree held itself up on limbs that landed on the opposite side of the driveway so that the car came out from under it completely unharmed. When I lived in town in Los Gatos, a massive coast live oak two doors down fell harmlessly into the front yard next door. The roots pulled up in front of and behind a Volkswagen GTI that was parked at the curb, and barely tossed an ounce or two of mud onto the hood. A few big olive trees did the same at a large condominium complex in San Jose during a windy storm, leaving nothing more than a bunch of leaves and olives on top of a classic Mercedes Benz sedan and an old Datsun B210. These are certainly not the only examples. This seems to be a common theme for these particular cars.
I can not say the same for Mercury, Plymouth, Jeep, Cadillac, Mazda, Toyota, Lexus, Honda, Subaru, Infinity or Volvo. I have never seen trees damage or avoid damaging them.
Damage to Ford, Dodge, Audi, Isuzu and BMW did not see to be targeted. It was the sort of random damage that one would expect from a tree innocently falling onto parked cars.
Both of the only two cars that I know of that were squashed while being driven were Lincoln Navigators. That is not a good statistic at all. One was hit by a falling Canary Island pine in Fremont. The other was clobbered by a Coast live oak in Saratoga. No one was hurt; but the cars were killed.
I have seen only one Chevrolet damaged by a tree, but it was vicious! It was one of only three coastal redwood trees in a landscape situation that I had ever seen fall, although ‘fall’ does not adequately describe what this tree did. Without enough wind to damage adjacent and notoriously structurally deficient California pepper and Chinese elm trees, this redwood seemed to jump out of the ground to land on top of an Astro Van about twenty feet away! I do not think the tree was targeting it because it was a Chevrolet. The tree obviously hated this specific Astro Van VERY much.
Acura seems to be the second most hated sort of car among trees. They are less common than Honda, but I have never seen a Honda damaged by a tree that it did not run into first. Yet, I have seen at least three Acuras destroyed by a coast live oak, a blue gum eucalyptus and a Monterey pine. That is an inordinate number!
The car that trees seem to hate most is Porsche! They are uncommon cars, and are probably less common than any other car that I have ever seen damaged or destroyed by trees. Yet, I have probably seen more of them destroyed than Acuras, including one that was attacked as blatantly as the Astro Van was attacked by the small redwood. The ONLY blue spruce that I have ever seen fall landed squarely down the middle of a new Cayenne, back when they were the first SUV that Porsche made. The densely foliated canopy enveloped the car so thoroughly that only the middle of the tailgate was visible.
It would be interesting to know if insurance companies have determined if any particular types of cars are more likely to be damaged or destroyed by trees than any other. I would think that if the trends that I have noticed are accurate, that insurance companies would be aware of them as well. I am also curious to know if other arborists have noticed similar trends.P80106



By modern standards, the public schools that I attended in the early 1970s would be considered to be bleak and primitive. The building were utilitarian and simple, from about twenty years earlier. The landscaping was comparably simple, with a big lawn and proportionately big shade trees. A screen of alternating Monterey pine and Monterey cypress was hedged on the southern half of the eastern boundary of the schoolyard. The only deviants to the simplicity were a few significantly older trees on the northern half of the eastern boundary of the school yard. There were two coastal redwoods, a Canary Island date palm, a cedar, and a spruce of some sort. They were all quite mature, and were likely remnants from an old farmhouse that was there before. Perhaps they wanted us to be aware that everything changes.
On the way to kindergarten, back when children were allowed to walk to school, I weaseled my way underneath the first Monterey pine and Monterey cypress on the southern end of the fence line, and fell asleep. I do not remember how long I stayed there, but it was long enough to get in serious trouble with my very worried kindergarten teacher. After that, I could only visit those two trees in passing, and perhaps stop only briefly to smell the foliage or shake some of the rain away.
Nearly four decades later, but only a few years ago, I was assigned the grim task of composing the arborist report that would justify the issuance of a permit to remove that same Monterey pine, which was the last that remained of the hedged trees that I remember. I did not know that when I went to the site. I was just told that it was a ‘pine’.
Visiting the old school was not a pleasant experience. The entire site was surrounded with a prison like fence and saran screens to obscure the view inside and out. There were no open gates. I needed to be escorted to the tree by a professional chaperone. Much of the schoolyard had been very synthetically landscaped with microtrees and pretty flowering shrubbery that was intended to impress parents rather than appeal to children. It is bad enough that there are no orchards or open spaces remaining in the region, but it is worse that children are deprived of the open lawns and trees and natural spaces that my generation had taken for granted on the grounds of our school. Are children even allowed to climb trees anymore? Do they know what dirt is? Can they observe a chrysalis split open to reveal a new butterfly before the gardeners shear the shrubbery and take the learning experience away? It was saddening.
Once I realized that the tree that I was expected to condemn was my old friend, I asked the chaperone, who seemed to know a bit about facilities at the site, why anyone would want the now mature tree to be removed. I knew that it had been mutilated while young, but was impressed with how it somehow recovered and developed a well structured trunk. I thought that perhaps someone noticed something that I was missing in my inspection. People who are not arborists are sometimes alarmed by something that is perfectly normal for a tree, such as furrowed bark, or slight seasonal foliar discoloration.
The chaperone explained that the tree needed to be removed simply because it did not conform to the style of the rest of the landscape. I waited for the rest of the answer, but that was it. The tree did not conform.
Nothing gave me more pleasure than to explain that after my evaluation of the health, stability and structural integrity of the subject, I could find no justification for removal.
I was dismissed.
Yes, it was worth it.
However, I knew that for the right price, another arborist would be pleased to condemn the tree. The picture of what remains suggests that the arborist who did so was not even professional enough to get his crew to finish the job. How does this dead stump conform to the rest of the landscape?
Those old trees, the redwoods, palm, cedar and spruce, were right. Everything changes.
The Monterey pine that would not conform is gone now, but it was right too.