Winter Injury
The cold, snow, frozen ground, and strong winds
of winter put even hardy New Englanders to the test. Just imagine the effects
on
our poor evergreen trees and shrubs. Many evergreens
suffer extensive winter damage and the
widespread effects are becoming noticeable. We expect to see damage on
moderately hardy species.
Winter injury can be
divided into three major
categories: cold injury,
desiccation, and salt injury.
The most common winter
injuries are due to extreme
cold temperatures. Low
temperatures can damage
or kill plants not adapted
to survive them.
Interestingly, the ability to
withstand low temperatures is not static. Plants
increase in hardiness during the late fall and early
winter. As spring approaches, hardiness begins to
lessen as plants prepare for the onset of active growth.
This is why sudden extreme low temperatures in late
fall or early spring are so damaging.
Desiccation, or
winter burn, is
another form
of winter
injury.
Desiccation
occurs when
sun and wind
cause water
loss in leaves
and needles of
evergreens.
A close up showing totally desiccated needles
which have lost all their moisture
winter when
soils are frozen or dry, plants are unable to replace the
moisture lost to transpiration resulting in the drying out
of leaf tissue. Symptoms include marginal browning
of leaves and needles, or in severe cases leaf death.
Desiccation occurs most often in late winter when
sunlight intensity increases.
Injury from de-icing salt is always a concern for plants located along sidewalks
and roadways. Plants even hundreds of feet away from heavily traveled roads
commonly suffer from salt spray damage. Salt injury to evergreens, especially
white pine, often becomes
apparent in late winter. Salt accumulating in the soil is
usually more damaging to plants than foliage burn. High salt concentrations cause
reverse osmosis; meaning water actually flows out of plant roots into the soil,
rather than the reverse.
Plants quickly dry out and can be killed. One challenge in diagnosing salt injury
is that by the time symptoms are apparent, spring rains have flushed the salt
from the soil where it may not be detected.
Plants that have suffered winter damage need special care. To insure optimal growth, plants should be watered, properly mulched, and fertilized if needed.
In cases of cold temperature injury, pruning should be delayed until the extent of the damage is evident.
How can winter injury be minimized in the future? Make sure the plants are adapted to their site. For example, if a plant is too tender for a sunny south-
west exposure, relocate it to a more protected location. See that plants are well watered and mulched entering the winter. A recent study by the
University of Massachusetts suggests moisture levels in September are especially critical. Protect plants with burlap, evergreen boughs, or simply have
Hartney Greymont apply a transparent film called anti-desiccant. These measures will help plants conserve water, and remain healthy and attractive
during difficult winters.
