Why Snow Causes More Tree Damage in Fall Than Winter

A fall snowstorm with light snow can take out an astonishing number of trees.

On October 29, 2011, the Mid-Atlantic and Northeast U.S. were racked by a Halloween snowstorm that no one took seriously until they woke up to blizzard conditions on Saturday. Tree damage from the snow was astonishing – from Pennsylvania to Maine, tree limbs crashed on power lines, taking out massive portions of local power grids. When the snow ended, every neighborhood in the storm’s track lost trees, and nearly 3 million households were without electricity.

Northeast Pennsylvania never saw significant snowfall in October – in fact, this storm was our heaviest October snowfall EVER – seven inches. The amount of snow wasn’t more than a typical winter storm – from 1 inch in the suburbs of Philadelphia to 26 inches in Massachusetts. But the damage to trees was devastating – more extreme than even Hurricane Irene in September. Only three inches of snow fell in New York City’s Central Park, but nearly one thousand trees were damaged or destroyed.

[su_highlight background=”#fff77c” color=”#00010b”]See pictures of the surprise October Snowstorm in 2011[/su_highlight]

What makes a fall snowstorm so destructive to trees?

The simple answer is leaves and warm temperatures. When snow falls in winter, much of it safely passes through a deciduous tree. The tree has dropped its leaves because it’s entered a winter dormancy period, which starts in late autumn. For the most part, a tree rides out the entire winter, storm after storm, intact.

When a snowstorm arrives in October with temperatures hovering around 32 degrees (as our storm in 2011 did), the snow is heavy and wet. Most deciduous trees have only just begun to drop their autumn leaves at that time. The early snow clings to the leaves, limbs, and branches at the top of the trees, which then act like a boat’s sail, catching the wind. This adds thousands of additional pounds of strain to the tree.

The weight of the snow forces limbs to bow towards the ground, exposing more branch area and more leaves, which in turn collect more snow, adding more weight. Decades-old, otherwise healthy trees snap under the strain. Just after the storm in 2011, I saw a tree that looked like it had exploded – the tree was split in half as if a giant had chopped it with an ax straight down the vertical center. All that remained was a three-foot jagged stump with the limbs, upper trunk, and branches splayed out from the center.

When a snowstorm comes in fall, remove heavy fall snow from your tree as soon as possible to minimize damage

[su_quote cite=”Dr. Ray Maleike, retired Washington State University Extension Horticulturist”] “When snow or ice bend branches and entire trees out of shape, the… snow or ice should be removed immediately and an attempt made to straighten the bent branch or trunk. If the plant part isn’t straightened very soon after the snow has stopped, the plant may remain bent over… permanently.”[/su_quote]

Unfortunately, there’s not much you can do to prepare your tree for an early storm aside from observing good pruning practices. But what you do after the storm’s damage is incurred is important.

Tips to minimize tree damage after a fall snowstorm

Remove the snow with a broom as best you can

Reaching as high as you can, move in an upward motion so you don’t put more tension on limbs. If a limb is packed with ice, let nature take its course and wait for the ice to melt. Trying to remove ice may cause more harm to the tree.

For arborvitae, restore its shape as quickly as possible

Some arborvitae branches may be bent out from the shrub. To get the plant’s shape back, carefully remove any snow, freeing the branch and gently lifting it upwards. You may have to tie the bent branches to the main stem to get them to grow back correctly. Use soft cotton clothesline and leave it in place well into spring. Tying the arborvitae plants together like this can be a good preventative before winter arrives.

If a small tree has bowed over but is not broken or split, stake it to save it.

Use two stakes about eight inches away from the trunk. Be careful not to damage or sever the roots when you drive the stakes into the ground. Tie the trunk of the tree to the stakes at the lowest point, which will stabilize the tree in an upright position. When the tree is able to stand on its own again, remove the stakes. The tree will usually stabilize during the first growing season after the damage occurred.