Nebraska Forest Service, Community Forestry & Sustainable Landscapes staff
Trees damaged by storms generally require some degree of immediate attention (removal of low hanging branches, clearance from utility lines, etc). Homeowners working on their trees need to be careful to watch out for safety concerns and to consider the best approach for dealing with the tree they are trying to save. Chain saw work off the ground and other heavy work (essentially all work on large trees) should be done only by professional arborists.
Hazardous Trees. Loose or loosely attached branches and split trunks are obvious safety concerns that should be taken care of as soon as possible to avoid the possibility of injuring someone or damaging property later when the branch or that part of the tree falls. Broken but firmly attached branches that pose no immediate danger of falling can be pruned whenever convenient after the more hazardous loose branches have been removed. Trunks split down the middle are very difficult to brace adequately, and trees with split trunks should be removed or taken care of by a professional arborist.
Power Lines. Branches hanging over, or near, power lines are a major safety hazard from any standpoint. Special training is required to prune branches near power lines safely. Homeowners should never attempt to prune these branches themselves. Contact your local power company or an arborist trained in electrical line clearance to have these branches removed.
Leaning Trees. The heavy weight of snow or ice may tip a tree over by breaking some of the roots. Trees leaning from root breakage usually do not survive well. If a tree tips or develops a permanent lean in a storm, it often means the tree had damaged or poorly developed roots before the storm pushed it over. If a leaning tree does survive, it often becomes a hazard from the damage it could cause if it were to fall. Mature trees rarely survive attempts to pull them back into place after being tipped over by a storm. These generally should be removed and replaced with new trees. Very young trees (typically less than 10 years in the ground) may survive if the trees are gently pulled back to their vertical positions. If this is done, avoid additional damage to the remaining roots if possible, press out any air spaces that may have formed in the loosened soil, water the area of the root system twice each week in the absence of rain during the fall, spring, and summer, cover the root area with two to four inches of wood chip mulch, and stake the tree for the first year to prevent the tree from falling again. Do not use rope, wire, wire in garden hose, or any narrow band of material to tie around the tree during the growing season. These will injure the trunk and could kill the tree as it tries to grow. Use a broad strap or other fabric at least one inch wide and inspect and adjust the location of the strap once each week during the growing season to minimize any injury the strap might cause to the bark.
Pruning. The only pruning that should be done at this time is the removal of broken branches. Leave the fine pruning and finishing cuts until later. All pruning cuts will dry out to some degree during the winter. Take care not to leave any stubs from your pruning cuts as these will not allow the tree to heal properly. Have a trained arborist make the final pruning cuts, especially on larger mature trees. Branches that have pulled away from the trunk should be removed at the bottom of the split. Avoid causing any additional damage to the trunk. Remove any loose bark or wood fibers, but do not cut into bark that is living and still attached. Never top trees, topping creates serious hazards and dramatically shortens the life of a tree. And never use paint or wound dressing to cover wounds. These materials do no good for the tree and actually interfere with the tree's wound sealing process.
Be Conservative. Do not prune or remove more than you have to at this time. Remove hazards, but save other decisions on pruning and removals for later. While the damage may look severe at this time, concentrate more on how to can save trees rather than making quick decisions on cutting them down. Keep in mind why you wanted your trees. The trees may still be able to serve that function. Don't be too hasty to make a decision to remove a tree if you can delay that decision to the spring or even a year from now. You may decide later the tree was not damaged as badly as you thought.
For more information, go to: http://www.nfs.unl.edu/ or http://arboretum.unl.edu/. A whole series on storm damage can be found at: http://nfs.unl.edu/documents/communityforestry/Storm%20Damage%20series%20entire.pdf.