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:

42 thoughts on “Six on Saturday: Untimely Death

      1. Hopefully, such pruning is concealed and never seen again. I think that this one only opened up because the wound was so big relative to the size of the remaining portion of the limb at the time.

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    1. Such deduction is sometimes part of my job. The decay here is irrelevant, but for some trees, it is what compromises stability and structural integrity. Sometimes, those who caused the initial damage are partly liable for incurred losses. Trees are a very valuable commodity, and are capable of causing significant losses.

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    1. I wrote an article quite a while ago about how careful many trees seem to be about landing where they will do the least damage, and when no one is around. There was another article, or it might have been the same, about how trees try to avoid crushing cars, but also seem to target certain cars that they dislike.


  1. Bass fishermen in some of the lakes north and east of here are being warned right now not to fish the banks, under the trees. There’s be so much rain and flooding that saturated soils are allowing pines and others to just fall over, even without wind.

    That diagram you provided is interesting. How trees are damaged and heal themselves is more complex than I’d really thought about.

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    1. I do not mean to state the obvious, but trees are not stupid. They put quite a bit of effort into healing their wounds. Those that are falling around the lakes are just unfortunate victims of their situations.


  2. That really was a small set of roots. A tree like that, I’d expect it much larger. That’s one of the things that happens here after heavy, prolonged rain–big healthy trees topple. Sad this one …

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    1. When I see such minimal roots, I look for the remains of decayed roots, but did not find any. This was the most disproportionately small root system that I have seen in quite a while. The fir that I wrote about later also lacked adequate root dispersion.


    1. If the wound had been smaller, and the tree had healed faster, the decay might not have been so extensive. It is actually quite normal for big oaks to be partially hollow inside. The main trunk of this particular tree was remarkably sound, with only the beginnings of decay.


    1. I believe that the majority of roots were underneath where the tree fell, so were obscured by the fallen trunk. Roots do strange things so close to the San Lorenzo River, which I should have mentioned, is only a few yards downhill. The area in the opposite direction of where the tree fell is always damp and smells funny, so may be saturated right below the surface.

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    1. Sadly, the wood will likely get used only for firewood. This species of oak is not commonly milled because there is no good lengths in it. However, it is not unheard of either. The priority is removing it efficiently. The trunks and main limbs will get taken to a wood yard. The smaller limbs get split first, so that if anyone finds a use for the larger bits, they can get them milled.

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