Winter is an ideal period for maintaining trees and shrubs. As cool temperatures prevail, many plants enter a dormant state. However, the frigid temperatures, coupled with the inclement weather, can create a stressful environment for plants, particularly those that are young, and have not become established. The following examines some of the best tree care practices one can utilize in winter. These practices will help plants survive the winter months, and ensure that they are prepared for the growing season.
In winter, heavy winds and a lack of available water can cause trees to experience drought conditions. Winter drought, also referred to as winter desiccation, winter drying, or winter kill, is detrimental to plants. It can inhibit growth, and reduce plant vigor. Evergreens are especially susceptible to winter drought, as they lose moisture through the pores in the underside of their foliage. Plants that have not absorbed ample water during the growing season may become desiccated. Plants suffering from winter drought often shed their foliage, and expire.
To prevent winter drought, ensure that plants are sufficiently watered until the ground freezes. This will enable the plants to absorb enough water to sustain them through the winter months. Warm spells may occur throughout winter. Occasionally this may result in a thawing of the soil, and plant roots. During these warm periods, the soil area of plants can be thoroughly drenched. This will help to stave off winter injury.
When planting, select a location with good soil drainage. Wet, poorly drained soil contracts and expands during winter. This can cause the roots to be heaved out of the soil. Root heaving is not as common in well-drained soils. During planting, sand and compost can be mixed into the soil to encourage drainage.
In fall, apply two to three inches of organic mulch around the base of plants. Proper mulching will improve the soil quality, while moderating the soil temperature, and retaining soil moisture throughout the winter months. Mulch also insulates plant roots, reducing the potential for root heaving due to harsh winter conditions. Ensure that there are a few inches of separation between the mulch and the trunk of the plant to discourage rodents from gnawing on the bark. Unless plants are diseased, or infested with insects, leaf and needle litter may remain on the ground. Cast needles and leaves provide an additional layer of protection for plant roots, sheltering them from the elements, while also conserving soil moisture.
Winter pruning, also referred to as dormant pruning, is beneficial to many trees and shrubs. During winter, plants can be more easily assessed for structural weaknesses. Healthy branches can be supported by removing dead wood, and thinning out a plant’s crown. Damaged or dead branches and trees should be promptly removed to prevent them from collapsing during snow or ice storms.
Removing Snow from Plant Limbs
Heavy snow and ice can cause brittle branches to crack and break. Evergreens are especially prone to breakages during winter. When snow or ice has collected on a branch, gently push it off using an upwards motion. Avoid forcing snow or ice off with a shovel, or broom. This can cause limbs to snap, or create wounds in the bark.
On young, soft-barked trees, and evergreens, trunks may be wrapped with a suitable fabric to prevent sunscald, or winter burn. Sunscald is a condition in which the sun causes a plant’s trunk to thaw during the day, only for it to suddenly freeze when the temperatures plummet at night. This causes the bark cells to rupture, inducing the formation of cracks in the trunk. Plants can be protected from sunscald with burlap strips. Each strip should wind diagonally around the trunk, and be secured with twine, or a similar material. These burlap barriers also provide limited protection to plants from salt spraying. Additionally, they may ward off small rodents that feed on plant bark during winter.
Plant Health Care
Trees that are vulnerable to winter burn can be treated with an anti-desiccant spray. The waxy coating created by the anti-desiccant will seal the pores on the leaves or needles of plants. This helps to prevent winter drought by limiting transpiration. Applications should be performed in late fall, and early February.
Fungicidal repellents can be applied to plants to discourage animals from feeding on the foliage, and bark. Fungicides are particularly useful for deterring deer. Repellents may be sprayed, or painted onto plants. The most effective method is to hang a rag, or cloth that has been doused in concentrated repellent near the plants in question. Repeated applications are required for continued success.
Preventing Salt Damage
Sodium chloride is often used to combat snow, and ice accumulation. While sodium chloride is a cheap and effective method, it can be detrimental to plants. Salt damage can be minimized by selecting a de-icing salt composed of calcium-chloride or magnesium-chloride. Magnesium chloride is one of the best alternatives to sodium chloride. It is effective at melting ice in temperatures down to 5°F. Calcium chloride can be used when temperatures drop below 5°F. While it is not as beneficial to plants as magnesium chloride, it is still considerably less harmful than sodium chloride. Beet juice may be used as an organic solution. When planting, consider using salt-resistant varieties, such as birch, black cherry, black locust, oak, and red cedar.
Photo courtesy of Amy Powroznik.