University of Illinois Extension
Watering trees, shrubs in the fall and winter is a balancing act
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[November 19, 2021]
After this year’s summer drought in Illinois, it is more important
than ever to monitor soil moisture conditions and water trees and
shrubs going into winter. Drought conditions in the late fall, along
with dry air and low soil moisture, can lead to plant damage if no
supplemental water is provided.
“If soil is dry, homeowners should consider watering their trees and
shrubs this fall and winter,” says Gemini Bhalsod, University of
Illinois Extension horticulture educator.
Plants under water stress are more susceptible to insects and
diseases. They can also experience injuries to roots or foliage.
Before watering, check the soil moisture. Monitor the moisture
levels about once a week. Dig a small hole under the tree's drip
line, 4 to 6 inches is enough. Feel for moisture. If the soil is
dry, the tree should be watered.
"This little bit of consistent effort will pay off in the long run,”
Bhalsod says.
In particular, newly fall-planted trees, shrubs, and perennials
should be monitored and watered late into the season, since they do
not have as much time to develop extensive root systems as anything
planted in the spring.
Pay attention to evergreens and shallow-rooted trees such as birches
and maples. Some shallow-rooted trees can be identified by roots
breaking the surface of the soil. Evergreens do not go dormant in
the winter and are still actively respiring and lose water through
their needles. Dormant trees respire at lower rates. Since soil
insulates and cools down later in the year than the air temperature,
roots stay warmer longer and respire at higher rates than the
above-ground parts, the trunk, and branches, of deciduous trees
after their leaves drop.
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Only water when the temperature is above 40°F. In some places, that could be as
late as the end of December. Stop supplemental watering after the ground freezes
because at this point the trees cannot absorb water through the frozen soil.
To water, use a soaker hose to provide a slow stream of water. Soil should be
moist, but not waterlogged. This method results in less runoff and the water is
more likely to be absorbed by the root zone. “If your hose is stored away and
your tree or shrub is small, pour water very slowly or drill a 1/8-inch hole at
the bottom of a 5-gallon bucket and fill that with water,” Bhalsod says.
Water at the tree’s drip line and not right against the base. To conserve water,
start with newly planted trees and shrubs weekly and then large and established
trees once a month if it is a dry period.
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Avoid fertilizer, which stimulates late-season growth, and instead, consider
applying mulch. Mulch can help conserve moisture over the winter months. Apply
mulch about 2 to 4 inches away from the base of the tree all the way to the drip
line in a doughnut shape around the trunk, leaving 2-to 4 inches of space in
between. As always, planting hardy species or cultivars with deep roots is best
since they are more likely to be able to survive temperature fluctuations and
prolonged periods of cold.
[SOURCE: Gemini Bhalsod, Horticulture
Educator, University of Illinois Extension] |