Trees may need 'first aid' after winter storms

A damaged tree on the OSU campus. (Photo by Denise Ruttan)
It's important to assess the severity of damage to trees and call a certified arborist when needed. (Photo by Denise Ruttan)
Last Updated: 
February 21, 2014

CORVALLIS, Ore. – After winter storms, it's time for the daunting task of cleaning up the damage.

Trees in particular can suffer the brunt of inclement weather, cautioned Paul Ries, an urban forester with the Oregon State University Extension Service.

"After the storm the task becomes triage, if you will pardon the pun, as people figure out the damage that was caused from the storm and what they can do to correct it," Ries said.

But there is some good news. Before February's snow and ice storms, Oregon had been experiencing a dry winter, which did not cause widespread soil saturation, Ries said. Waterlogged soils can deprive tree roots of oxygen and affect root growth, which can destabilize the whole tree. Instead, February's storm brought light, powdery snow and ice that broke lots of tree limbs but did not spell total disaster, he said.

Don't try to repair all the damage yourself if your trees are large, Ries advised. Bring in a certified arborist if large limbs are broken or hanging.

"I tell people that if the corrective measure involves using a chainsaw off the ground, then it's time to hire a professional," Ries said.

But there are actions that you can take on your own. First assess whether the tree can be saved with these questions:  

  • Is the tree healthy other than the storm damage?
  • Are major limbs broken? The larger a broken limb, the harder it will be for the tree to recover.
  • Has the leader – the main upward-trending branch on most trees – been lost? In some species, a leader is important to upward growth and desirable appearance.
  • Is at least 50 percent of the tree's crown – or its branches and leaves – still intact? A tree with less than half of its branches remaining may not be able to produce enough foliage to sustain itself.
  • How big are the wounds where branches have been broken or bark has been damaged? The larger the wound, the less likely the tree will be able to seal off the damage.
  • Are there remaining branches that can form a new branch structure?
  • Is the tree the most suitable species for the location?

It's time to say goodbye if disease has already weakened the tree, if the trunk is split or more than 50 percent of the crown is gone, Ries said.

If the damage is light, prune any broken branches. Repair torn bark or rough edges around wounds by using a sharp knife to cut away jagged edges. Rough edges around wounds can invite insect and disease problems, so it is better to cut the broken branch off cleanly rather than leave a stub, Ries said.

Also, don't "top" or cut back all of the branches on trees, Ries cautioned. Topping the tree will reduce the amount of foliage on which the tree depends for the nourishment needed for re-growth, he explained. The branches that sprout out from topping cuts will be weaker than normal ones, meaning the tree is more likely to develop a structural defect if it has been topped. 

After pruning, give your tree time to recover. Trees are injured for life and cannot heal themselves in the same way that humans regenerate tissue after a cut, Ries said. Eventually new wood grows around the injury and seals it off; it’s the tree's way of defending itself against wounds, he explained.

The best time to prune trees is in their dormant season, Ries said. Trees usually remain dormant from mid-November through mid-March.  

For more information, see the Oregon Department of Forestry fact sheets that Ries helped produce, Tree First Aid After A Storm and Can These Trees Be Saved?. Also view the Arbor Day Foundation's storm recovery website.

Author: Denise Ruttan
Source: Paul Ries