Frost cracks in a tree.
Frost cracks in a tree.
The recent winter storms has provided some needed precipitation, but last week it has been dry with above average temperatures.

So, how does this winter weather affect your landscape plants? And what can you do to prevent any winter injury?

Winter injury to plants is a common problem throughout Nevada. Damaged plant parts dry out, die or become diseased; ultimately, the whole plant may die.

Dry soils, dry winter winds, warm, sunny days and freezing nights without precipitation contribute to winter plant damage.

Most plants continue to lose moisture during the winter. Water loss is greatest during windy, sunny, mild weather.

If the ground is frozen below the root zone, water is unavailable to plant roots. Consequently, internal plant water becomes Inadequate to compensate for that lost from the plant.

Leaves of broad-leafed evergreens curl inward and hang down when water loss exceeds uptake.

Under severe conditions, leaves “burn” at their margins, turn brown and dry out. Well-adapted, narrow-leafed evergreens, such as yew, spruce and juniper, and many non-evergreen trees and shrubs, also suffer winter desiccation injury.

Daily heating and freezing accompanied by wind and bright, sunny skies, damages exposed limbs and trunks, most commonly on their south and west sides. Sunburned and dehydrated bark splits, cracks and dies, especially if the plants have thin or young bark.

Flower buds of many plants may abort over winter, eliminating spring flowering. Leaves, buds and twigs may desiccate. If water stress is prolonged, the entire plant may die.

With our current weather I would be most concerned with winter wind and sun stress (Frost Cracking). When direct winter sun heats the plant, the temperature of bark and twigs exposed to direct sunlight exceeds air temperature.

Daily freezing and thawing of plant parts causes cracking, drying and death. Reflected sunlight from light-colored buildings, fences, soils and snow may also stress plants in winter.

Even hardy plants exposed for long periods to bright conditions are often damaged if soil moisture is unavailable.

Temporary windbreaks, plant covering and shade may be erected for the winter using lath snow fence, screening or burlap plant wraps. Wrap evergreens with burlap and pull the branches together to reduce water loss. Cover small plants with a slotted peach basket or clothes basket anchored to the ground.

Use anti-desiccant or anti-transpirant sprays during the winter to prevent water loss from evergreen plants. Periodic applications may be required depending upon the amount of precipitation, wind, sun and the length of the winter season. These products are available at local nurseries.

Even though landscape plants are dormant and brown, they should be watered periodically.

Dry winter months often kill plants through dehydration. Consider these tips when winter watering:



When to water

• Choose a warm winter day with air temperature above 40 degrees F and unfrozen soil.

• Water one to two times per month from November to April.

It is most critical to water in March and April when the new roots are forming.

• Water at mid-day so it can soak in before it freezes.



What to water

• It is most important to water newly planted lawns, trees and shrubs.

• Established lawn areas and trees, especially those in sunny, windy, or exposed areas should also be a high priority.



How to water

• Use a hose-end sprinkler or watering wand since automatic sprinkler systems are off during the winter.

• Remove the hose from the spigot after watering to prevent freeze damage.

• Water slowly so it can soak in.

• To figure out how long to water, put out cups to catch some of the water. Water until you can measure 0.5 to 1” deep in the cups.

The best prevention of winter injury is to select plants that are hardy in your area. Winter damage can be reduced by locating plants in partially shaded areas protected from winter winds.

Place physical barriers about 18 inches away on the windward side of young trees to reduce winter injury.

Barriers made from materials such as burlap or plastic can lessen winter wind damage by reducing wind velocity.

Maintain adequate soil moisture in the fall to prevent winter desiccation. Inspect plants for winter damage in the spring and prune out affected areas.