Rock salt damages evergreens, including airborne salt from nearby vehicle traffic.
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Many contractors and homeowners use salt deicers to combat ice on roads and sidewalks. While salt stains are a common sight
on cars and steps, many may not know that salt deicing products can also damage foliage on trees.
Sodium chloride, the scientific name for rock salt, is the most popular and generally least costly type of deicer. Unfortunately,
as ice and snow treated with rock salt melts, the resulting runoff may cause harmful byproducts to seep into soil or splash
onto leaves, causing wilting and other injuries to vegetation.
"It is impractical to avoid salting completely because safety on our roads and sidewalks is obviously an important issue,"
says Dr. Bruce Fraedrich, vice president of research at Bartlett Tree Expert. "However, there are ways to protect trees and
shrubs." Fraedrich points to several causes and telltale signs of deicing problems, and offers solutions:
- "A lot of trees are affected by airborne salt kicked up by traffic. It settles on leaves, desiccating the tree. Some trees
absorb the sodium and others suffer from root damage, caused by salt seeping into the soil." Species most susceptible to this
type of damage are evergreens, including conifers, pines, spruce and holly trees. Fraedrich says trees retaining foliage year
round have the highest risk.
- Professionals can identify damage by the wilting and dryness of leaves and other foliage, though symptoms are usually evident
only after large masses of salt have accumulated. "Damage to the soil can be spotted by noticing significant drooping, especially
at the top of a tree, because salt inhibits absorption of water by the root system. Salt damage produces similar symptoms
as drought. When caused by airborne salt (from vehicles), it usually occurs on the lower part of the tree, facing the street,"
he says. Damaged trees also tend to have thinner leaves and often bloom later in the spring.
- Other symptoms include stunted growth of foliage, browning of foliage, thinning of branch tips, premature fall coloration/defoliation
and dead branches. Severe cases often lead to insect infestation.
"Damage is hard to prevent and winter weather complicates efforts to help trees, because there's no way to wash off salt,"
says Fraedrich. To counter the inevitability of salt damage, Fraedrich recommends planting trees tolerant to salt (such as
birch, oak or juniper) near the road and driveway. Beyond that, he advises monitoring plants to ensure their overall health.
"Keep trees well watered and use gypsum (calcium sulfate) to help counteract salt in the root system," he says. A certified
arborist can help keep trees healthy year-round so they are less susceptible to winter issues. Other measures can be taken to reduce the risk of damage including diverting salt from trees by erecting barriers of burlap
or wood, laying down mulch to prevent seepage and watering during dry periods. These preventative measures can decrease the
chances of trees experiencing heavy damage.
— For more information, please visit Bartlett Tree Experts at http://www.bartlett.com/ or call 1-877-BARTLETT.
