|
 Boxwood, arborvitae, and other evergreen species
have leaves and needles that transpire water all year long, even in
winter. When water exits the plant faster than it is absorbed,
winter burn occurs in desiccated needle and leaf tissue. Water loss
happens more quickly in windy or sunny conditions, even in low
temperatures. Without wind protection, more damage may be noticed on
the windward side of the plant, typically the south or southwest.
"When autumn doesn’t provide enough rainfall, deep watering before
winter increases moisture to the roots before the ground freezes,"
says Sarah Vogel, University of Illinois Extension horticulture
educator. "You can provide water during brief thawing on warmer days
in winter to further lessen winter burn."
A ring of mulch around the base of the plant provides a layer of
insulation that helps maintain moisture, reduce drastic soil temp
fluctuations, and prevent frost heaving. Mulch should stay a few
inches away from the trunk.
Burlap or canvas windbreaks may reduce injury from wind, however, if
injury is sustained year after year this greatly impacts the overall
health of a plant, and different species may be considered for the
site. High levels of stress, such as repeated winter injury,
increase susceptibility to biotic pests and pathogens.
Anti-desiccant sprays help retain moisture and protect plants from
some fungal diseases. Prune away any damaged tissue before new
growth emerges in spring.
Another issue is sunscald and frost cracking. Frost cracking occurs
when the sun warms bark and outer wood, causing it to expand. In the
absence of sunlight, temps cool, and that same tissue will contract.
These sudden temperature fluctuations result in vertical fractures
along the trunk, called frost cracks.
Sunscald is a result of the same conditions but causes a different
type of damage. Tree cells enter dormancy during winter months.
Dormancy can be disrupted by direct sunlight warming cells, only for
temps to drop again and kill tree cells. [to top of second
column] |
These phenomena occur in young, thin-barked species
such as maple, ash, linden, apple, and peach. Young trees with no
barrier from elements are more susceptible. Providing adequate water
through fall and winter will help prevent sunscald.
Planting trees where they will be protected from the
late afternoon sun helps to prevent sunscald and frost cracking. If
using tree wrap, apply wraps in November and be sure to remove them
in April. Leaving wraps on all year can cause damage or restrict
growth.
Winter often brings snow, ice, and high winds which puts branches at
risk of breaking. Removing snow loads by shaking branches is not
recommended. In fact, it can lead to further damage in frozen,
brittle branches. Gently remove snow by using a broom and sweeping
upward, but do not stand under the branch. It is best to wait for a
warmer day or until the ice melts.
Some trees are more susceptible to broken branches in winter
conditions, like multi-stem trees, upright evergreens, and
especially trees with included bark from co-dominant stems or narrow
branch angles. Prevent storm damage before the risk of breakage is
present by pruning deciduous trees while they are young. Remove
codominant stems and promote an appropriate scaffolding structure.
Avoid pruning late in summer as it promotes new growth that cannot
harden off before winter. This can lead to frost damage dieback on
branch tips.
If branches break in young trees during a storm, prune them back to
the main branch or trunk. Seek help from tree care professionals to
prune limbs of larger trees.
Trees are a large part of any landscape and keeping them healthy by
using good cultural practices is the best preventative measure
against pests, pathogens, and natural disasters. Use these methods
to prevent winter damage and protect health of your trees. For more
information, review this
Trees and winter storm damage article.
[Sarah Vogel, Horticulture and
Natural Resources Educator, University of Illinois Extension] |
