Damage from winter is the perfect embodiment of the can, the can’t and the discernment thereof. Sure, there are several prevention and recovery steps that one can take, but there’s also a certain level of understanding that life sometimes tosses things at you that you simply can’t control.
In the design phase
Sustainable landscaping, resource-efficient plantscapes or plant health care all start with a sound design, forethought and common sense. One of the techniques in this regard is proper placement of woody plants from day one.
As trees are identified in the potential landscape, the usual considerations of strategic placement for shade benefit and separation of trees and turf are crucial to its success. Placement is also important in terms of preventing winter injury. Generally, fewer incidences of damage occur when trees are colocated with other woody plants and as far away as possible from hardscape elements such as driveways and parking lots. Thin strips of landscaping that contain trees are problematic in that they produce greater temperature extremes; don’t allow for adequate rooting, water infiltration or oxygen exchange; and often facilitate injury from deicing salts.
Several techniques for preventing winter injury or at least lessening the potential for damage exist. The things you can control category includes:
Proper planting of new trees — Volumes have been written on proper tree planting and its positive effects on the survival of trees. In short, digging a hole that is at least twice as wide but no deeper than the root mass, planting a 1-inch-caliper tree instead of a 6-inch spaded specimen, taking the time to spread out tangled roots in the planting hole, and placing the root mass at or slightly higher than the grade will go a long way toward helping a new tree make it through that first winter.
Proper watering of new and existing trees — For both new and existing trees in the landscape, adequate soil moisture is essential for winter survival. When roots are not hydrated, they wither and die; the more roots that are lost from lack of moisture, the less chance a tree has of making it through the winter in good shape. New trees should be slowly watered around the root mass until the soil particles are thoroughly moist. Drip irrigation devices work well for this purpose.
Of course, as with most good things, too much can be problematic. In this case, watering too much or too often will exclude soil oxygen and cause root decline. The key here is to keep the soil moist, not soggy or dry. Knowing where the roots are for existing trees is essential. Keeping them moist with soaker hoses is an effective method of preventing root dieback.
Antidesiccants — Lightweight horticultural wax products can help trees, especially evergreens, weather the winter. On average, three applications made six weeks apart can keep the needles/leaves full of moisture and prevent winter drying. They’re of particular value when the soil is frozen for extended periods and for trees located in windswept areas.
A couple of caveats with antidesiccants: they must be applied to foliage when the temperature is above freezing so they can dry on the leaf surface, and the sprayer used to apply them must be thoroughly cleaned out after the application.
Shields — Especially on the south and west side of trees, shields will help prevent damage from winter sun. Warm winter sun often causes a softening of the conductive tissues within a tree trunk.
This is most common on thin-barked trees such as Norway, red and sugar maples. The softening is a form of de-hardening, which would not be a problem if winter were over and spring arrived the next day. However, when it occurs in midwinter, the cells are damaged when subfreezing temperatures are experienced that night. Preventative shields reflect the warming rays of the sun, keeping the inner tissues cooler and lessening the effects of the temperature fluctuation. Shields that are white in color are more effective than dark-colored materials in terms of reflection potential.
Mulch — Well-placed wood chip mulch (spread at least out to the edge of the crown) helps prevent winter damage in several ways. A 2- to 3-inch-deep layer of mulch slows down evaporation of moisture from the soil. It also helps keep the soil and tree roots cold and constant, instead of dry and fluctuating. Ensure that the mulch is not in direct contact with the trunk, otherwise the potential for rodent damage is high.
Actions taken during the winter can be just as helpful as preventative steps before winter.
Antidesiccants on days above freezing — Antidesiccant spray applications should continue during winter as long as conditions are cold and windy. A thorough preventative application at the onset of winter is a good step, but it’s usually not enough. On average, two additional applications are required. Thanksgiving, Christmas and Valentine’s Day are good guidelines for timing.
Winter watering — On days when the temperature is above freezing, water when the soil is thawed out enough to accept it. Avoid overwatering, as too much water will create a layer of ice, preventing oxygen availability as much as an impervious surface will.
Inspect for frozen snow — Rabbits, squirrels and other small animals can walk on frozen, compacted snow and use it as a platform for chewing bark on tree trunks. Taking the time to displace the snow around high-value specimens may be necessary to avoid damage to trees and shrubs.
Inspect for mouse damage — Damage from mice and other rodents can be severe, especially around new tree trunks. The guards and shields mentioned earlier are also helpful in reducing damage from mice. Inspections should be made during winter as necessary to prevent injury.
Flushing applied salts — Damage from deicing agents can be lessened by flushing them from the soil surface. Sodium chloride can cause significant burning to the root tips and hairs. Rock aggregates can become incorporated into the upper layers of the soil, decreasing its tilth and friability. Making repeated applications of water in spring can physically remove deicing agents, lessening their negative effects.
Pruning affected limbs — Despite all of your best efforts, there may still be some winter damage, including branch dieback. Once it’s obvious that a particular limb will not continue to grow and produce healthy leaves, it’s necessary to remove it so the tree can direct energy into the other limbs.
Sometimes it takes a wake-up call to see the value of good arboricultural practices. In the case of winter damage, explaining the importance of preventative and ongoing maintenance procedures to customers can lead to a win-win situation: more business for the arborist and healthier trees for the client.