When living with wintry snow and ice conditions, the safety of roads and pedestrian walkways are the first priority. However, application of de-icing salt can wreak havoc with the health of your property’s lawn, trees, and shrubs.
How Salt Damages Plants and Lawns
Sodium chloride — refined rock salt — is the cheapest and most ubiquitous de-icing material. Unfortunately, it’s also the most harmful one for your plants and lawn. When salt-spray and salted snow from road trucks is deposited on the bark, leaves, and needles of nearby trees and shrubs, it can cause bud death and branch dieback. When sodium chloride melts the ice and snow on walkways, driveways, and roads, the salt mixture filters down into the soil and prevents the plant roots from absorbing the available ground moisture, a condition called “chemical drought.” Salt on the plant or in the soil generally impedes development of new leaves and results in gradual loss of plant vigor. Salt in the soil can cause also compaction, which disturbs the plants ability to absorb moisture and nutrients.
It’s not easy for the untrained eye to recognize the symptoms of salt injury since they mimic the signs of drought damage. In both cases, discoloration of the leaf occurs. However, it appears on the leaf’s edges in the instance of salt damage, and throughout the leaf when drought has taken its toll. The best way to assess any damage is to have an arborist perform a general inspection.
How to Reverse Effects of Salt Damage
The key is to reverse salt damage early. So once the temperature is above freezing, spring into action!
- The spring rain will help wash off the accumulated salt on plant foliage and flush out salt buildup from the soil. But it’s good to help Mother Nature along. Once the weather warms up, rinse off all plants adjacent to salted walkways and roadways, and water them thoroughly to dilute residual salts (give plants about two inches of water over a two- to three-hour period, and repeat a few days later.)
- Lightly prune any dead twigs, needles, and small branches on salt-damaged trees and shrubs. If the shape of the plant has been compromised, contact your arborist for a rejuvenation pruning of the entire plant.
How to Prevent Salt Damage
- The best way to prevent salt damage is to avoid using de-icing salts completely. Instead, remove snow and throw down clay kitty litter or course construction sand for traction.
- If you do use a de-icer, choose a non-salt option. Calcium chloride is shown to be less toxic to lawns and plants than sodium chloride (but know that the absorption of chloride ions can still be harmful to plants). Better still is calcium magnesium acetate (CMA). Know that both of these de-icing alternatives are more expensive than rock salt. A compromise is to mix these more expensive de-icers with sand or kitty litter.
- Install a barrier to keep salt off the roadside areas of your property, such as temporary snow or silt fencing, or a tight planting of salt-resistant shrubs.
- If your property is located in an area that will likely get salt from municipal road-salting, plant salt-tolerant tree and shrub species. Your local arborculturist can suggest the best ones for your grow zone.
- Have your arborist apply an antidesiccant in the fall which will form an invisible protective coating on leaves, branches and bark. Pay particular attention to evergreens which line the street, since they are especially vulnerable.
- As always, keep your trees and shrubs healthy to improve their resilience to salt spray and soil salts.
Janna Beckerman and B. Rosie Lerner, “Salt Damage in Landscape Plants,” April 2009, Purdue University Extension, https://www.extension.purdue.edu/extmedia/id/id-412-w.pdf
Tom Butzler, “Salt Spray Damage and Evergreen Plants,” Penn State Extension, January 19, 2017, http://extension.psu.edu/plants/green-industry/news/2017/salt-spray-damage-and-evergreen-plants
“Winter Protection of Trees and Shrubs,” Cornell Cooperative Extension, Rockland County, May 2011, http://monroe.cce.cornell.edu/resources/winter-protection-of-trees-and-shrubs
[Author name unavailable], “Gardener, Spare That Tree (From Salt Damage),” New York Times, February 23, 1989, http://www.nytimes.com/1989/02/23/garden/gardener-spare-that-tree-from-salt-damage.html