While diseases are important in plant health, they are not responsible for every browning or plant death. Abiotic diseases can cause problems too. Things like drought, freezing temperatures, herbicide drift, dog urine, nutrient deficiencies – anything negatively impacting plant growth that isn’t caused by a living agent. That includes salt, the kind used for deicing purposes in the winter.

Most people know by now that rock salt can be harmful to pets - causing lethargy and vomiting if ingested and irritating little paws just by walking on treated surfaces. It also damages plants, and spring is the most common time of the year to see the effects; that’s when the telltale signs appear. Leaf or needle browning, bud death, and scorched-looking leaf margins are all typical. When you look at the whole plant, branch dieback on the side facing a road or sidewalk may be evident.

Some signs, though, are not apparent until summer, when deicing is but a faded memory. Summer is when fewer or smaller leaves than normal can be observed, and water stress becomes a concern. These symptoms occur more often in hot, dry years. The salts in the soil can absorb water, making it less available for the plant. Then roots dehydrate, and the damage may not be fully visible until summer.

Plants are exposed to these salts through a variety of ways. Sometimes they are inadvertently applied directly onto plants, especially if located near a sidewalk or roadway. Other times, spray from passing cars lands on plants, and salt-laden snow can even get plowed or shoveled onto landscape plants. In these cases, rock salt desiccates bud scales, the protective layer around buds, leaving tender floral and leaf tissue exposed to the ravages of cold, winter winds. In milder winters, the impact may not be as pronounced. But in winters with a wicked polar vortex, don’t be surprised if damage is more apparent.

However, one of the more destructive introductions comes from salts dissolved in runoff water, creating the potential for salt accumulation in the soil. Chloride can accumulate at toxic levels in plants, leading to interference with chlorophyll production and ultimately a lea- burn appearance and dieback. Sodium and chloride together cause nutrient imbalances in soil. Roots will absorb sodium & chlorine instead of other, essential nutrients like phosphorous and potassium. This results in problems such as darkened, discolored leaves or yellowing between leaf veins.

If you are concerned about this kind of damage, changing the type of salt you use may make a big difference. All salts are not created equal. Most just happen to be rock salt, which is made up of sodium chloride and is the most damaging to plants. Other, safer options include magnesium chloride, calcium chloride, and calcium magnesium acetate. Salts without sodium are preferable around plants (and pets!) and important tools for preventing future damage.

If you can’t control the type of deicing agent used, consider changing your landscape. Some plants are more tolerant of salts than others, such as juniper, Mugo pine, white spruce, paper birch, and sumac. These would be better suited for locations near sites treated with salts in winter.

The extent of damage depends on the plant type, movement of runoff, availability of fresh water, and the type of salt used. There are many kinds of deicing agents available for use on roads, driveways, and sidewalks. Chemistry matters in this case.

In addition to rock salt,

• Salts applied late winter more damaging than early apps (allow more opportunity for salts to leach away before growth in spring
• Volume of fresh water applied to soils impact amount of salts leached away, rainfall washes salt from leaves

Management: reduce salt use

• Combine salt with sand, sawdust, or cinders that can provide grittiness for traction
• Use calcium chloride, magnesium chloride, potassium chloride (more expensive)
• Target apps away from plants & beds
• Flow of runoff should be considered
• Protect plants with physical barrier – burlap, plastic, wood
• In times of warfare, used to destroy soils

There are many kinds of different salts available in winter for use on roads, driveways, and sidewalks to manage snow and ice and make surfaces safer for driving and walking.

Dr. Jill Calabro
Research & Science Director
Horticultural Research Institute & AmericanHort

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