Managing Woody Plants in Winter

By Michelle Medaris, LCDBM

Trees that are bent over by snow have a chance at recovery, but it largely depends on the percent of bend. A tree with less than 20 degrees bend will recover, and a tree with less than 60 degrees bend has a good chance of recovery, but a tree with more than 60 degrees bend has a low chance of recovery.

As the winter season is now upon us, tree care can become a more complicated task. Winter storms make trees not only susceptible to damage, but also death. Here we will examine the havoc winter storms can cause, as well as how to treat the resulting problems.

Winter storms include rain, wind and snow, but it is the wind and snow that can cause the most damage, such as, bending, breaking, splitting, and falling or uprooting.

Bending
Bending by snow often happens in smaller statured or younger trees that do not have the trunk strength to shed heavy snow loads. For a smaller tree, it is recommended that the snow be shaken off as soon as possible, however if the tree has been completely bent over it is best to wait until spring or warmer weather to see if it will stand back up on its own.

If a larger tree has been bent over because of snow, wait until the snow melts and see if it will come back to the upright position. If it has had enough water during the previous season, it may straighten itself back out.

Do not try to straighten a tree out during colder temperatures of winter (unless your area does not get sustained freezing temperatures), this action can damage the tree and cause it to break if the inner fibers are close to freezing temperatures.

It is natural for trees to bend in the wind; as a matter of fact, a tree able to move in the wind has a better chance of survival than one staked down. However, if a tree stays in a bent position after a windstorm, action may need to be taken. In this case it is best to consult an arborist who has wind damage expertise.

In a sense wet snow that breaks off twigs and dead branches is pruning the tree, but it is a good idea to follow up with clean cuts.

Broken or Breaking Trees
Either the weight of snow, wind force, or both can cause a broken or breaking tree. A broken or breaking tree is one that has torn wood fibers, either on the stem or branch. At times broken branches can be completely torn from the tree, or still hanging by one or two fibers. Regardless of the cause, this scenario is extremely dangerous, and must be dealt with immediately, by cutting off the branch.

Most broken branches can be pruned, but it is important to monitor the tree's health, as the tree becomes more vulnerable to diseases.

In this case pruning is the answer, although larger broken branches can rarely be salvaged, smaller branches on smaller trees may be mended, depending on the amount of damage. A mended branch may be a weaker area of the tree, and it is suggested to prune to a smaller size for the life of the tree.

Depending on the severity of the split in a tree, treatment may be as simple as pruning or as drastic as having the tree removed.

Splitting
The cause of splitting branches or stems comes from the action of forceful winds twisting the tree or branch, which can cause cracks or actual shearing (tearing) from the tree.

During a windstorm the form of the tree can also be a major factor in splitting, as trees with co-dominant stems (two or more main stems about the same size in diameter, which have emerged from the same location on the main trunk) are structurally weaker.

Another structural consideration is included bark within co-dominant stems; this is when bark is embedded between opposing branches, a branch and a main stem, or two co-dominant stems; thus making the tree even weaker.

Snow can be a contributing factor in splitting, as the weight of snow causes additional stress.

Breaks, tears and cracks are difficult to repair without certainty of future branch or tree strength, and can be destructive to the overall tree health. Depending on the damage to the tree, splitting may be remedied by pruning, however if it is not something that can be fixed with pruning, you may need to call a consulting arborist for further instruction.

Attempting to save an uprooted tree can be costly, and often times the tree is removed at a later date, however smaller trees have a better chance of being salvaged.

Falling/Uprooting
There are many factors that contribute to a tree falling or uprooting, however consulting arborist, Ruben Green of Evergreen Arborists Consultants, said, the correct amount of pruning makes a huge difference in the health and life of a tree.

The general rule says not to remove more than 25 percent of a tree when pruning. However, if a tree is not pruned at all, it becomes top heavy and it may topple over in a heavy windstorm. If a tree is over-pruned it does not absorb the wind as well, thus making it susceptible to failure.

How Snow Helps Trees
Snow can also help trees and woody plants, according to Tchukki Andersen, staff arborist with the Tree Care Industry Association (TCIA), "Snow is both friend and foe to trees and shrubs. Although snow can cause damage, in many cases it also protects plants and their roots against extreme fluctuations in temperatures."

Snow can moderate root temperatures and provide moisture for spring; it also helps insulate the ground, which is beneficial for two reasons:

First, snow is a poor heat conductor, so the temperature changes very slowly from the top layer of the snow to the bottom. This keeps the ground from heating and cooling as air temperatures fluctuate.

Second, heating and cooling often cause the ground to heave, which can be damaging to roots. Keeping the ground temperature more constant is a better environment for healthy roots. A covering of snow can help keep the ground warmer. Pile eight inches of snow on the ground and soil temperature seldom falls below 23 degrees.

For more information about tree health and safety visit the Tree Care Industry Association (TCIA) at tcia.org or American Consulting Arborists (ASCA) at asca-consultants.org. These are great resources for arborists, as no two scenarios are the same.