The winter season has arrived; the temperatures have dropped, the trees are entering dormancy, snow is flying and plow/salt trucks have been deployed. These typical winter conditions can affect the overall health of your plant material. Applying a few preventative maintenance strategies now may significantly reduce injury or loss of landscape plant material.
Sunscald and frost cracks can be common occurrences in northern Illinois; both occurring when temperatures drop, both resulting in cracks. Winter days offering sunny warmth, heats the surface of the tree trunk, causing it and the inner tissues to expand. When the sun is blocked by a cloud, building or sunset arrives, the temperature of the trunk drops quickly to that of the ambient air resulting in the trunk contracting. The outer part of the trunk cools and contracts faster than the inner tissues. This difference in rates causes pressure toward the outer trunk resulting in a crack.
Frost cracks almost always develop vertically and most often are found on the south or west side of the tree, but can occur on all sides. Sunscald, also favors the south and west sides of a tree, but typically appears as elongated, sunken, dried, peeling areas of dead bark. The peeling/cracking of sunscald is not limited to vertical formation. Newly planted, young and/or thin barked trees are most susceptible to both injuries.
To help reduce the occurrence of cracks, wrap the trunk with commercial tree wrap, plastic tree guards or any other light-colored material. Protective wrap should go from the base of the tree to the first lateral branch. The wrap reflects the sun helping to maintain a more constant temperature of the bark. Wrapping should be placed on the tree in the fall and removed in the spring after last frost.
Evergreen foliage can become brown or bleached during the winter months due to excessive transpiration (movement of water from roots, thru vascular system, into atmosphere.) When the soil becomes frozen, the roots are unable to take up and replace the water lost during this process. Foliar damage is most seen to the south, southwest or windward sides of evergreen trees, but in severe cases the whole plant may be affected.
Constructing a barrier can help to minimize winter injury to evergreens. A barrier made of burlap or similar material, on the windward or vulnerable sides of the evergreen, twelve to eighteen (12-18”) inches away from the plant, can help reduce the impact of drying winds. If plant material requires fencing to all sides, be sure to leave the top open to allow for air and light penetration.
Trees adjacent to vehicular and pedestrian thoroughfares are exposed to additional factors that may result in damage. Salt spray generated from de-icing services after winter storm events often result in dried/damaged plant parts. Trees located near usable pavement may fall victim to unnecessary loading on limbs/bows due to snow thrown from plows or shovels. The above mentioned technique of constructing and installing a barrier fence will also help to deflect potentially damaging snow and salt.
Periodically throughout the dormant season, it is recommended that installed protective measures (burlap, trunk wrapping, etc.) are inspected to ensure they are properly in place, have not been damaged and are still present.
Anne DalrympleKramer Tree Specialists, Inc. ISA Board Certified Master Arborist, IL-4275 BT