GardenLine | Trees and Shrubs | Preparing Trees and Shrubs for Winter

Wood is an instructor with the Department of Horticulture Science. This column is offered as an extension service by the Division of Extension and Community Relations and the Department of Horticulture Science, University of Saskatchewan.

Though our problems with drought have lessened this year, it is still important to prepare trees and shrubs for winter by watering them adequately. In response to dry conditions, evergreens, notably cedar, pine and spruce trees, can produce a dramatic needle shed. Some needle shed is normal with all evergreens, but dry conditions cause an increase in needle shed. Deciduous trees can be affected by dry conditions, as indicated by increased seed production, poor leaf growth and early defoliation.

Because evergreens lose moisture from their needles, which are retained year-round, they tend to be more susceptible to dry conditions than deciduous trees, which lose their leaves. It is therefore especially important to water evergreens well before winter.

A Recommended Watering Method

All trees should be well watered in the fall as a routine practice, with special attention to those showing drought symptoms. Some homeowners believe that trees located on lawns will receive adequate moisture if the lawns are watered well. Not so! The sod will use most of the water, leaving very little for the trees.

The watering procedure for trees is simple. Lay a soaker hose on the ground in a circle under the "drip line" of the tree, an imaginary circle projected onto the lawn by the outer ends of the branches. Most of the tree's feeder roots are located under the drip line. The distance from the soaker hose to the trunk (the radius of the drip line) may be 1, 1.5 or even 2 m, depending of course on the size of the tree.

Punch a number of small holes in the sod, using a hollow pipe or potato fork. Punch these holes along the edge of the soaker hose. Then turn the hose upside down over the holes so that it soaks directly into the soil rather than spraying into the air. Turn the water on very slowly and allow it to soak for about 8-10 hours. The objective is to saturate the area under the tree without runoff or puddling. Punching the holes in the lawn will improve penetration of water to the tree roots.

Timing - Use the watering procedure described above on trees every third or fourth week during the summer. During September the trees should be soaked once. This will allow them to harden-off in preparation for winter. Excess moisture in September can induce the trees to produce new succulent growth which would likely die during winter. Finally, give the trees a last soaking in late October, after they are fully dormant but before the ground freezes. Also at this time, all shrubs should be soaked thoroughly.

Protection from the Elements

Strong winds during the winter and spring draw moisture from evergreen needles. As a result, some needles will turn brown and die. To protect low-growing plants such as cedar shrubs, junipers and perennials from drying winds, construct a burlap or cardboard windbreak, or erect a snow fence around the plants. The fence will also help capture snow, which provides excellent protection and insulation for low-growing junipers and perennials. In addition, you can pile snow lightly around the plants during winter and early spring. Watering plants in winter to coat the leaves with ice can cause damage to the plants and so is not recommended.

Lawn Care

Now is the time to prepare your lawn for winter. Late fall fertilizing is not recommended. Fertilizing may stimulate the lawn to continue growing and so it is not desirable at this time of year. If the fall has been dry, give the lawn a good soaking just before the winter, when there is no chance the lawn will grow. Ample moisture now will help to prevent desiccation of the lawn during winter. Remember to take the leaves off the lawn. Grass that is protected by leaves will not harden-off properly and so is more susceptible to winter injury. In late fall, keep cutting your lawn at the 5-6 cm height. Long grass will often mat under the weight of the snow, and this can cause severe damage by smothering and diseases.

---

Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.