Broken branch on a street tree
Fall is upon us and winter is just around the corner; it’s a good time to check the health of your trees. Large trees are important assets and shouldn’t inspire fear, but it is wise to hire an arborist for pruning and/or inspection periodically. In all cases, knowledge of tree species and familiarity with their weaknesses is important. It is also important to hire an ISA-certified arborist. Beware of tree companies that canvass your neighborhood; they may lack the knowledge, experience, or insurance to work safely and may instill fear in residents for their own gain. For more information about finding an arborist:
http://www.isa-arbor.com/faca/findArborist.aspx
Below is list of tree defects or signs of stress in each portion of the tree. Arborists inspect trees methodically and can recommend mitigation if defects are found. Note that this is a simplified list, each tree is different, and experience is an important factor in identifying tree defects.
Canopy
Look for dead, damaged or hanging branches, branches that are not strongly attached to the trunk of the tree.
Mitigation: prune dead, broken, or poorly attached branches off. Remove ivy or other vines that add weight to branches.
Trunk
Look for decay, fungal fruiting bodies (not moss or lichen growing on the bark), cavities, areas where the bark has fallen off, and cracks in the trunk.
Mitigation: determine the extent of decay and whether the tree is creating new wood to support itself. If a high percentage of the trunk is decayed, removal may be the only option.
Roots
Look for fungus growing around the base of the tree; large numbers of dead branches and sparse canopy in the summer can be a sign of root problems.
Mitigation: excavate around the base of the tree, working carefully to keep healthy roots intact. If a large percentage of roots are decayed, removal may be the only option.
Soil
Look for cracks in the soil around the tree, soil mounded up on one side of the tree combined with a leaning tree.
Mitigation: if there have historically been drainage problems in the past, make sure all gutters and drains are in good condition and working properly. Saturated soil is a prominent cause of soil failure. If the tree is actively failing (leaning with soil movement) and is too large to be staked upright, removal is the only option. Note: It is easy to look at a tree and wonder, has it always been leaning like that? An experienced arborist can look for signs of recent movement. It can help to take pictures of your trees to document changes over time.
More winter tree care information: http://www.seattle.gov/transportation/wintertrees.htm