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What might indicate a tree is at risk of falling?

We encourage residents to act as a Neighborhood Watch for The Park's street and island trees, especially after big storms and soil saturating rains. As the police say, "See something, say something" -- but what to look for?


Here's specific guidance from San Mateo's City Arborist: 

"When we have extreme weather, there is no guaranteed method of predicting tree failures like the ones we have seen in San Mateo Park. Once the soil is saturated the overall stability can be compromised. This can be difficult to identify as it can happen to healthy and, under normal circumstances, stable trees.


The idea of seeing something and saying something can be a valuable tool. When residents are out in the neighborhood they can look for the following things that may, although not for sure, indicate a tree is at risk for failure: - Soil that is heaving or looks disrupted and uplifted immediately around the base of the tree in question. - Noticeable cracks in the soil around the trunk of the tree and extending out several feet. - A distinct change in the angle of the tree from its previous position. - Any notable decay, fungi or mushrooms growing at the base of the tree or the surrounding area.


It can be difficult to predict when these trees might fail, but if we inspect suspicious activity, we may be able to remove hazardous trees before they come down on their own."


The City arborists can be reached at 650-522-7420 or


If you note any of these developments around trees on your property, it would be prudent to consult a certified arborist.  

Oak tree on Occidental island toppled during storm January 27, 2023

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