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Poor tree architecture or structure stands at or near the top of the list of tree failure causes. Many failed trees are removed at very high cost in built landscapes. Pruning is cheaper than tree removal, and if properly executed, can prevent premature tree removal and extend tree life span. Therefore, pruning, when done correctly, stands as one of the most sustainable tree inputs. On the other hand, pruning can cause structural and health problems for the tree when done incorrectly.

How these failures occur:  1 | 2 | 3 | 4 | 5

Trees that become large lack good mechanisms to cope with the spreading habit when the crown is raised off the ground. Many trees also are not well adapted to maintain the upright, multi-leader habit. Their mechanical and biological properties are inadequate to support these forms because these is very different from their natural habit. Several defects can arise: 1) Bark inclusions, a serious defect rare in the moist forest, is common in the union of large branches on open-grown trees. This was the cause of the failure shown above. 2) In response to crown raising, low aggressive branches (limbs) and stems grow up at an angle into the permanent crown in a manner unfamiliar to most trees. They can crack or break as they grow long and heavy (The permanent crown is that portion of the tree that will remain for a long time). 3) Other branches may sag and get in the way requiring their removal after growing quite large as show on the left. These three conditions can lead to a shortened life from cracks, broken trees, and trunk decay.

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