Protecting Evergreens from Winter Injury
Evergreen trees, such as spruce, pine, cedar and juniper, are hearty and stay green all winter. Nonetheless, they’re susceptible to injury unless they have the proper care. Browning of evergreens in the spring is a sign of winter injury. Here are some ways to help prevent evergreen winter injury in your trees.
What’s Evergreen Winter Injury or Winter Burn?
Sunny winter days with above-normal temperatures may be a welcome treat for you, but they can harm your evergreens. Evergreens keep their needles all year, so they always need moisture. Warm temperatures and high winds strip evergreens of precious water, and their needles become too dry. Since the ground is frozen, the tree can’t replenish the lost moisture, resulting in winter injury, also known as winter burn or winter browning.
Recognize The Symptoms of Winter Injuries
Trees may look green and healthy all winter and will only show signs of winter injury in spring. Symptoms of evergreen winter injury will vary depending on the evergreen type and the severity of the moisture loss. Damage is usually more severe on plants in exposed, sunny locations and branches above the snow line.
The most common symptom is the needles turning a light tan or reddish-brown. Discolouration occurs at the tips and moves down the needle on pine and spruce. Branch tips of junipers and cedars (arborvitae) may die. The scale-like leaves of the cedars look pale and bleached when damaged. The plant may lose most needles on one side or over the entire plant if the injury is severe.
Do Junipers Turn Brown in Winter?
Junipers don’t generally turn brown in winter, but their leaves can turn brown due to winter burn. However, discolouration in junipers may also be a symptom of Kabatina tip blight, a fungal infection. It’s best to call a professional arborist to distinguish between the two.
Causes of Evergreen Winter Injury
Cold temperatures alone generally don’t injure plants. Evergreen browning is often caused by rapid temperature changes, above-average temperatures and warm, dry winds. Warm temperatures may also cause damage by breaking the dormancy of plants.
The warm, dry winds experienced during chinooks, for example, increase the amount of water lost from the needles. Plants on the south side of buildings or in exposed areas are more prone to injury.
Moreover, young evergreen trees with shallow root systems are more prone to winter injury because it’s more difficult for them to extract moisture from the frozen ground. Trees have a better chance of avoiding winter injury if their roots go below the frost line.
How To Prevent Evergreen Winter Burn
Since you can’t control the weather, total prevention of evergreen browning is difficult. But proper maintenance of trees and shrubs and planting species hardy for the area will significantly minimize the damage. Here are some evergreen winter care tips.
- Plants should be adequately watered throughout the growing season. Trees and shrubs require a minimum of 50 millimetres (2 inches) of precipitation per month during the growing season. Young trees with shallow roots require more water.
- Reduce the amount of watering in late summer (mid-August until late September) so that proper hardening-off can occur. Then, give plants a good watering just before freeze-up. When the soil freezes and hardens is when to stop watering cedars, junipers and other evergreens for winter.
- Avoid pruning evergreens in late summer or fall, as late-season pruning can encourage new growth that won’t harden before winter.
- Protect your evergreens by wrapping them loosely in burlap, canvas or snow fencing to protect them from direct sun and wind. Place one to 1.5-metre stakes half a metre from the tree’s drip line and wrap the material around the stakes, leaving the top open. Remove the material promptly in the spring.
- Mulching increases moisture retention and prevents alternate freezing and thawing of the soil. Mulches should be pulled away from tree trunks in the fall to allow the plants to harden correctly.
- Don’t apply excessive amounts of nitrogen fertilizer in late summer and fall. This will promote succulent growth that may not mature before winter.
- For cedar (arborvitae) and juniper winter care, plant these trees in the right locations. Avoid planting cedars and junipers on the south- or west-facing sides of buildings and fences. Junipers are highly sensitive to reflected sunlight and warmth from a building’s surface, especially bricks, concrete or metal siding.
And remember, when you plant new trees, choose species that are adapted to our conditions.
Spring Care for Evergreen Winter Burn
Winter injury will seldom kill a tree. An evergreen showing signs of winter injury should be well watered as soon as the ground thaws. Light fertilization will help stimulate the plant but should be applied only after signs of new growth. Injured trees are slow to begin growth; therefore, pruning should wait until you’re sure which branches are dead.
Evergreen Winter Care in Calgary, Edmonton, Kelowna and Winnipeg
At ArborCare®, our certified arborists can help prevent evergreen winter injury for your trees. As part of our plant management program, we can apply a winter spray coating that acts as a waxy layer of protection for your trees. To book a tree assessment on your property with one of our arborists, contact us today in Calgary, Edmonton, Kelowna and Winnipeg.