Limit winter damage to your plants
Photo by Creative Commons Zero
You’ve prepared for the predicted snowstorm. You’ve spread salt on the driveway, sidewalk and steps, reducing the chances of slipping and falling.
However, have you considered how your lawn and plants will fare this season? A little bit of science provides reasons to prepare your garden for the damage of winter weather.
Chemistry: Slippery surfaces
Chloride-based chemicals (salts) are applied to impermeable surfaces to melt ice and snow. Salts commonly used are sodium chloride (table salt or rock salt) and calcium chloride.
Typically, we apply these compounds before precipitation falls. Because a brine (salt and water mixture) has a freezing point lower than water, it melts the ice and helps prevent the formation of more ice as temperatures drop.
However, plants are injured when roots and foliage are exposed to salt water. Salt damages vegetation by increasing stress similar to drought conditions, affecting the quality and mineral content of the soil and accumulating to toxic levels within plants.
Spring rains usually flush salt from soil. If there’s unusually low precipitation during the spring thaw, you can dilute the salt in your lawn and on your plants with a garden hose.
However, once plants show symptoms, it is too late. Symptoms of salt injury include brown or dropping needles on evergreens, sparse leaf production on deciduous plants, brown leaf margins throughout the summer, and even death.
Sodium chloride can burn a lawn if the concentration is too strong. Calcium chloride is less harmful than sodium chloride, but may still cause plant injury.
Over time, concentrated salts in the soil may cause progressive decline leading to the eventual death of plantings. Rutgers University Cooperative Extension has compiled a list of plants especially sensitive to salts at plant-pest-advisory.rutgers.edu.
As an alternative to salts, if paths are icy, consider using sand, bird seed, plain clay cat litter or sawdust for traction.
The Cornell Cooperative Extension recommends using a mixture of three-parts sand, sawdust or kitty litter mixed with one-part calcium chloride. These mixtures manage sidewalk ice and snow effectively; however, they are messy when tracked indoors.
Another alternative is calcium magnesium acetate, which is biodegradable and environmentally friendly, but expensive.
Biology: Frozen lawns
Deicers may cause lawn grasses to turn brown or die back; you usually notice this in a strip close to a sidewalk or road.
Another winter concern is foot traffic on frozen lawns. When a lawn is covered with frost or snow, the grass blades are literally frozen. As a heavy object, such as a mower or a person, presses down onto the grass, the expanded water molecules cause significant cellular damage inside the blade.
You can see the results of the damage when the crushed blades turn a white or beige color. The lawn will probably recover, but not before spring.
Physics: Snow- and ice-covered shrubs and trees
Snow itself is not dangerous to plants. In fact, it’s a natural insulator, protecting plants from freezing and thawing temperatures. Therefore, leave the snow unless it is too heavy and bends branches severely.
The best technique for removing snow is to gently brush upward with a broom or lightly push limbs upward with a pole. Be careful when standing underneath taller shrubs or small trees while you do this.
Do not shake the shrub or tree, as this can cause more injury, especially to evergreens. If snow is frozen on the branch and doesn’t brush off easily, let the snow melt naturally to avoid damage.
When shoveling or blowing snow near shrubs, avoid piling excessive amounts of wet, heavy snow on them, as the weight of compacted snow can break branches.
If foundation shrubs are located underneath roof eaves, you can protect them by constructing A-shaped wooden frames and installing them before bad weather arrives.
Upright shrubs such as arborvitae, Leyland cypress and some junipers may splay outward under the weight of snow. You can reduce the effects by giving support: tie strips of cloth or twine around the shrub, or tie the leaders together inside the shrub to maintain its shape. Don’t forget to remove the supports during growing season.
Relatively little can be done to prevent ice damage. It’s typically better to let ice melt naturally.
As soon as weather permits, prune any limbs damaged by ice and snow to prevent ragged tears of the bark. Wounds with clean edges heal better.
Winter is a great time to inspect trees for dead branches, crossed branches, or overhanging branches where falling limbs may cause a problem. If these are higher than you can reach from the ground, call a professional for preventative pruning.
Lela Martin is a Master Gardener with the Chesterfield County office of the Virginia Cooperative Extension.
