Dakota Gardener: Tips for assessing storm damage

Joe Zeleznik, Forester
North Dakota State University Extension
Joe Zeleznik, NDSU Extension forester

When I was in college, I enjoyed country music a lot.

In the late 1980s, Tanya Tucker had a No. 1 single titled, “Strong Enough to Bend.” The song relates strength to flexibility, with the analogy of a strong tree and a strong relationship. Both the partners in the relationship and the tree need to be strong enough to bend during difficult times.

I like the analogy, though I’m much more of an expert with trees than I am with relationships!

Though trees are tough, resilient and long-lived, some storms are so strong that trees can’t bend enough. Too much snow or ice, or extremely strong winds, sometimes harm our trees in the Great Plains. The damage might be minimal or it could be a major problem.

Safely inspecting tree damage

While your first instinct might be to go directly to your trees and start cleaning up the debris, remember this important safety precaution: stay away from downed power lines.

In addition to the lines being energized, trees and branches can sometimes conduct electricity as well, and you could be severely injured through indirect contact via stems and branches. Wait until the professionals have cleared the way and made it safe to work on or near the trees.

Once it’s safe, assess the damage to the trees. Often our response is to simply prune back a few broken branches, calling it good. Surprisingly, making proper pruning cuts is the number one way to help a tree on its way to recovery.

A proper pruning cut reduces the chances of an insect or a decay-causing fungus from entering a tree. There are a lot of great resources available for pruning, including the International Society of Arboriculture’s website.

How much damage is too much?

While cleanup may be as simple as picking up broken twigs, the damage might be substantially worse. Perhaps one or two large branches came down. Were major limbs torn from the trees? Is the main stem intact, or was it cracked and twisted, and unlikely to recover?

This really is the million-dollar question. Branches hold the leaves, and the leaves are what make sugar during photosynthesis. I call them the tree’s “food factory.” That food factory normally gets bigger each year as the tree itself grows larger.

Then the storms come along and knock that factory back. Again, how much is too much?

This green ash tree lost a major limb that was beginning to decay from the inside. Removing the tree was an easy decision, says Joe Zeleznik, NDSU Extension forester.

There are no hard-and-fast rules on tree damage. We must assess the damage for each tree individually and make our best evaluation of how to proceed.

I often begin with the rule-of-thumb for pruning young trees – remove less than about 25% of the branches, and therefore the leaves, in any given year. Pruning more than 25% and the tree begins to feel some stress.

We can follow that guideline with storm damage as well. If less than a quarter of the crown is gone, the tree will likely not even feel it. Just clean up those broken branches and walk away.

Will a tree survive the loss of, say, 25% to 50% of its branches? It's likely, though it will feel some stress. Take care of it during the following year or two by watering as needed and controlling pests when they arrive. The tree will be stressed and will grow more slowly, but it’s likely to survive.

When to remove your tree

When a tree has lost more than half its crown, though, is when I start to worry. Can it recover?

While we can’t predict the future, we do know that trees with this amount of damage will be suffering major stress. They will be highly susceptible to insect and disease infestations in the following years, and might begin to slowly decline.

It’s a difficult decision, but after that amount of damage, it might be time to remove the tree.

As I said earlier, there are no hard-and-fast rules. We have to make our best guesses and go with them. Can we find examples of trees having recovered after losing more than half their crowns? Yes, but we can find many more examples of trees going into decline and dying following this amount of damage.

Is there a bright spot in all this? Yes. If we remove trees, that means we can plant new ones to take their places. And that’s a cause for hope!