As the snow piled up on the driveway, I thought about all of the garden plants that would be harmed by the salt that is often spread to make driving safer. At our house, we take the "put 'er in 4-wheel-drive and go" approach, so we don't salt much. But for many people who live along a city or county thoroughfare, injury to plants is a real concern.
Salt injury on many plants can resemble drought stress, with symptoms of scorched yellow or brown leaf edges, according to Bill Hlubik, a professor and agricultural resource management agent for Rutgers Cooperative Extension in New Jersey.
On evergreens, symptoms can appear rapidly and needles will turn yellow or brown from the tip. Deciduous trees and shrubs may show stunting, yellowing and curling in April or May, as trees begin to leaf out.
As a side note, salt acts like a desiccant and will dry out and crack animal paw pads - house pets are particularly susceptible.
Much of the salt used is sodium chloride. When salt is applied to the surface of roads and sidewalks, it dissolves into the cold, moist surface and separates into sodium and chloride ions, according to Hlubik. Sodium ions that reach the surrounding soils can lead to compacted soils, by displacing calcium and other nutrients that help maintain healthy soil structure.
The compacted soils have less oxygen available for roots and may not drain properly, leading to the decline of plant roots and overall plant health. The chloride ions are taken up by plants, and can accumulate in leaves and needles to toxic levels.
Excessive salt use also may lead to nutrient deficiencies with potassium and magnesium, which are important for chlorophyll and food production in plants. Improper or excessive use of salts may lead to poor quality soil and plant damage.
The combination of these two factors, with repeated salt exposure, can damage and sometimes lead to the death of sensitive or weakened trees and shrubs, as well as other perennials. Excessive salt and fertilizer use also may cause a serious ecological imbalance and harm beneficial organisms in soil and water.
Of course, you can use less salt. Some people use sand, but it doesn't dissolve and there is controversy as to its efficacy. A salt and sand mixture is often used.
Some alternatives that work include calcium magnesium acetate and potassium acetate, which are more expensive than sodium chloride. Some homeowners use urea, which is used for deicing on airport runways. It is a common fertilizer ingredient that provides nitrogen, but it doesn't break down easily. Also, it can cause algae blooms in waterways, so don't use it near a stream or pond.