Why some trees fall while others stand tall in storms

Proper pruning helps prevent failure

High winds often snap pines while oaks tip out of soaked soil. (News 12 Westchester, Inc. via CNN)

JACKSONVILLE, Fla. – Wet soil and high winds make trees dangerous in storms but pruning and other factors can make some trees safer than others. 

The deaths of a reporter and photographer in North Carolina on the fringe of Subtropical Storm Alberto reminds us about the danger of topping trees in high wind storms. Both men were killed in their news van when a tree crashed to the ground.

Gene Bushor with Bushor's Tree Surgeons has owned the Jacksonville business for over 50 years. He can't talk specifically about what happened to the news crew in North Carolina, but talked about how tree roots weaken during heavy rain.

"The roots themselves are stationary, but when you get the saturation of so much rain and a combination of the limbs being one-sided, the tree can fall without wind just for no reason whatsoever because there’s no anchor in roots," Bushor said.

We remember how Irma knocked down many trees around Jacksonville. Many were aided by saturated wet soil. These conditions typically uproot trees rather than snap in half.

But even with little rain or wind it is possible for trees to topple if the roots are decayed because roughly 90 percent of a tree’s roots are in the upper 18- 24 inches of soil.

Pruning can make top heavy tree canopies less dangerous according to researchers at the University of Florida.

They tested the wind resistance of pruned live oaks in 110 mph wind shooting out the back of airboat fans and found trees grown with good trunk taper and wide spacing are less susceptible to breakage than trees with poor taper. 

Trees in thinned stands can develop good taper, root systems, larger crowns, and result in better stability compared with trees in denser stands.

But it is important to prune correctly since lifting the crown high off the ground makes trees fail more often in windstorms. 

All trees will eventually fail depending on the strength of the wind but some species thrive in high winds better than others.  

Palms survive wind better than broad-leaved trees and conifer trees. Pine trees can mask damage after high winds, and lose strength over time and can pose a risk long after the storm clears.

It can be hard to spot visual clues revealing which trees are high risk for falling.

Recent leaning or cracks in the stem can be an indication of issues. Root problems are often reflected in crown condition so look for a healthy crown with full foliage in the growing season and good bud set for the winter. 

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