Been trimming all types of trees for 30 years. I'm no expert just want to care for all the trees I planted over the years …over 150…. to protect them from harm. ie: disease/ storms an property. Most trees are trimmed to be sail-worthy for winter storms and trimming out any crossing branches and thinned out for adequate airflow. I have a small tree collection of various species of trees in the PNW.
The rule of thumb for trimming trees from working with trained arborists over the years is to never thin or clear out any more than 1/3 of the canopy from any tree. There are a few exceptions…removing too much from a tree especially if not well established can cause the tree to go into to shock without enough leaves for photosynthesis to support part or the whole tree . The best time of year to prune evergreen/deciduous trees is late fall or when they are dormant.
In my experience if enough of the root system is destroyed or detached, the tree will die. As a general rule, 20% of the root system can be destroyed before the tree will show any signs. In my garden gophers, ground squirrels have damaged tree roots gnawed roots off leaving only two main roots as long as the main root is not damaged the trees is ok. Then by examining the tree and why it's is leaning in this particular case is done by carefully digging around the tree root area and discovering nubs left that were chewed on roots. I have managed to save a few small trees with roots eaten more than 40% from the total root by carefully replacing the soil under the small tree then supporting and secure the tree in place. Blocking the entry to the tree with traps and catches the gophers.
When all else fails and considering the safety of any tree call a Certified arborist. Sometimes just a minor trim is all that is needed. Every year in the PNW we hear of a tree falling on a home, car or other property that could have been prevented .
OK maybe a bit too long …
