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Protecting Trees and Shrubs
In nature, trees and shrubs take care of themselves · the
strongest survive and the others become part of the cycle of life. In
our yards, we rely on our plantings to enhance and beautify our personal
environment. We use plants in our landscapes that wouldn't naturally
grow in that setting or in our climate. To help insure that our trees
and shrubs have a good chance to do their best, we often have to provide
protection for some plants from our Michigan winters. Methods of
protecting trees and shrubs in winter vary, depending on the type of
damage you are trying to prevent.
What
causes winter damage?
Cold temperatures, ice/snow, wind, salt and animals can all cause
considerable damage to your trees and shrubs.
What kind
of damage is caused by cold?
If your plant is marginally hardy in our climate, cold temperatures
alone can kill back the tender tissues. But even hardy plants can be
damaged by sun scald, winter browning of evergreens, die back, root
injury, and heaving.
What is
sun scald?
Even on the coldest winter day, the sun can reflect off the snow onto
landscape plants and warm the tissue enough to thaw; then the sun sets
and the temperatures drop, freezing the plant tissue again. On young
trees, this alternate freeze/thaw cycle can causes vertical splits in
the bark on the trunk. This is a problem on most young trees, but is
most common on maples.
Can I
prevent sun scald?
You can wrap the trunks of susceptible trees and prevent almost all
splitting. There are several kinds of tree wrap available. The easiest
and least expensive is a neutral brown color and comes in several length
rolls. You simply start wrapping around the base of the trunk and work
your way up as far as you can reach or to the lowest branches. You can
also get plastic tubes that can be slipped around the lower section of
the trunk, but they can leave too much of the trunk exposed.
When
should I put on the tree wrap?
Tree wrap should be in place before the snow flies and off as soon as
the snow is gone. Protect your tree every winter until the tree has
begun to develop a thick bark (this may be several years).
Is there
anything I can do if the bark has split?
Splits usually don't cause any long lasting damage. Carefully trim off
any dead bark. It won't reattach itself and will be a site for decay.
Wounds that are elliptical in shape, like a football, will heal the
quickest. Unless the tree is an oak or elm, pruning paint or sealer is
not recommended. The tree will form a callous around the edges of the
wound that will grow toward the center.
What
causes evergreens to brown in the winter?
When it is windy and sunny in the winter, evergreen foliage can lose
moisture that it cannot replace with the ground frozen, resulting in
browning. To help minimize this browning, be sure your plants have been
well watered all season, right up until the ground freezes. Avoid
planting evergreens in a windy location where the receive the direct
afternoon sun in the winter.
How can I
protect evergreens from winter-burn?
The only way to protect trees that are planted were they might
winter-burn is to put up a barrier of some sort. A loose-weave burlap
can be wrapped around the plant or stretched across stakes in the ground
forming a screen.
Is there
anything I can do if my plants have been winter-burned?
It's best to wait until the new growth develops in late spring before
taking any action. Brown needles will not recover and will either be
shed or have to be pruned out. New growth may cover much of the damage.
Keep the plant well watered and fed throughout the growing season.
What
about the ice and snow?
Evergreens can be damaged by heavy snows or ice buildup. On trees such
as spruce, the branches will usually bend and recover. Plants with
upright branching such as arborvitae and junipers, can split and break.
Can I
prevent ice and snow damage?
Sometimes it's possible to reach inside evergreens and tie branches up
with something soft. (Panty hose are great for ties, since they are
strong, flexible, soft and don't degrade readily.) On smaller landscape
plants, you can wrap the outside loosely, like lacing a shoe.
I've
heard animals can damage landscape plants. Is that true?
Actually, rodents and deer can do extensive damage to trees and shrubs
as they forage for food during the winter. Rodents can be kept from
gnawing on trees by encircling the base of the trunk with 1/4"
guage hardware cloth or screen wire. The wire cylinder should be tall
enough to extend at least a foot above the deepest expected snow. When
this isn't practical or possible, you may want to try using repellents
such as Tree Guard, Ropel or Hinder. Tree Guard is more expensive, but
will stick to the plants for several months at a time.
Is there
a good way to keep the deer from chewing on my landscape plants?
Unless you can fence the deer away from your plants, you will have to
use a repellant. Most of the commercial repellants work either by giving
off an offensive odor (such as Deer Away).
Is there
anything I can do to prevent salt damage?
While there are some varieties of plants that are tolerant of low levels
of salt, nothing will withstand very much. In fact, salt can actually be
used as an herbicide. Avoid planting where salt will be used or where
there might be salt runoff.
Will
mulching help my plants make it through winter?
Mulch can definitely help minimize damage done to the roots by the
alternate freezing and thawing that takes place in late fall and early
spring. Apply 4-6 inches of shredded leaves, bark, hay or straw in late
fall, once the ground is cold and leave it on until mid-April.
Can the
ground get too cold for my plants?
Yes. And in Michigan plants, we rely on receiving adequate snow cover to
insulate the ground from the colder air. Winters when we don't have
enough snow, the root systems of many hardy plants can be damaged.
What
causes die back and is there anything I can do about it?
Sometimes our winter weather kills the tips of branches on trees and
shrubs. Tender growth and flower buds often receive the most damage.
Avoid fertilizing later than mid-August, so growth will have time to
harden off before winter. Die back will have to be pruned out in the
spring or early summer.
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