Is My Tree Healthy?

IMGP5372As an arborist consulting the public, this is the question I am most frequently asked. The answer should be an objective, blended assessment of the tree’s structure and its vitality. A tree with excellent structure but poor vitality will usually be showing signs of distress. A tree with excellent vitality but poor structure is another story. Sometimes I am called to give a quote to prune such a tree and the owner is shocked when I identify structural compromise that affects the rating of its condition. “But it’s so beautiful,“ they say, “the tree is obviously healthy.” A lot of vitality can also mean a heavy canopy, which can exacerbate the risk of failure at the structurally weak point.


Even the biggest tree hugger on the planet can’t safely prescribe mitigation in every instance in the urban forest. You can forgive tree lovers for occasionally being deaf to answers they don’t want to hear. Therefore, if mitigation can’t bring a tree to an acceptable risk level, and the owner doesn’t want to remove it, I will not work on it at all. To do otherwise would be misleading, creating a false sense of security. At the end of the day, the owner and the public are the ones living under that risk. Arborists can propose mitigating the risk whenever it is a reasonable alternative, but they should quantify the residual risk, not tell you it “will be fine,” and they should inform you of the frequency and protocol for ongoing regular review and care. Mitigation is seldom a one-shot-deal.


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Many factors go into quantifying the risk a tree presents. By far the most important is TARGET. What will your tree harm if it fails? How frequently is the target in proximity to the tree? Can the target be repaired if harmed? Replaced? Removed? Sometimes, even moderate risk is beyond the risk tolerance threshold of the land use. Like at a nursery school playground.


Trees are living organisms exposed to environmental conditions that can bring about sudden changes to vitality and structure. A perfectly healthy tree with perfect structure presents minimal risk, but not zero risk. Helping trees achieve the best possible structure enables them to enjoy long lives and provide sustained benefits for the communities around them.


So the next time you ask if your tree is healthy, listen for a two-part answer.



Jose Rubio Lazo

Ontario Urban Forest Council