Slipping and falling on ice hurts. We’ve all done it, and many of us dread going out in wintry weather for fear that it will happen again. In the US, we spread around 20 million tons of salt annually on roadways, parking lots, and walkways to keep us safe from ice. We all breathe a sigh of relief when we fall in line behind the salt truck on our commute to work, or when we hear the crunch of salt underfoot as we make our way across the grocery store parking lot during a storm. Unfortunately, salt remains in the environment long after the ice melts resulting in negative impacts to waterways, and biological systems including our landscape trees, shrubs, and turf.
Salt injury to plants occurs in two ways:
- Salt spray kicked up by vehicular traffic is carried through the air causing foliar burns on evergreens. Eastern White Pine is very sensitive to volatilized salt injury.
- Concentrated salt water moves from impervious surfaces to soil where it impairs plant roots. This salt-induced barrier to water moving into plants is referred to as “physiological drought.” A loose analogy would be a castaway at sea. So much water and nothing to drink. Sugar maple and hemlocks are examples of trees that do not tolerate high soil salt concentrations. Also, weeds tolerate salt better than turf grass making areas along sidewalks predisposed to more weeds.*
For an array of reasons including public safety, we in northern climates won’t stop using salts for melting ice any time soon. However, there are things we can do to use less salt, including the obvious – USE LESS SALT:
- Temporarily restrict access in some places instead of salting.
- Mix sand with salt in a 30:1 ratio to sufficiently lower melting temps of ice while improving traction.
- When possible, mechanically remove ice and snow from impervious surfaces by plowing and shoveling it off before conditions become icy.
- Use Calcium, Magnesium, or Potassium chloride instead of the cheaper rock salt, Sodium chloride as it is less harmful to plants.
- Calibrate and maintain salt dispersal equipment to avoid excessive salt usage.
Consider the following cultural practices to avoid salt damage to landscape trees, shrubs, and turf:
- Install trees and shrubs that are tolerant to salt spray near heavily traveled roads.
- Redirect runoff from salted surfaces away from priority landscapes by regrading or creating berms.
- Install tree and shrub species that are tolerant of salty soils where such runoff is unavoidable.
- Avoid plowing salt-laden snow onto the root zones of trees and shrubs.
In the event that salts have damaged landscape trees shrubs and turf:
- Identify the cause of plant damage to prevent or minimize it from happening again.
- Flush salty soils with water in the spring as needed. A soil test should be taken to confirm salt concentrations. DO NOT flood poorly drained soils.
- Prune out branches damaged by foliar burn.
- Contact a qualified arborist or turf specialist to diagnose the problem and prescribe a mitigation plan.
The bottom line is, we do not want to sacrifice public and personal safety, but we need to be aware that our actions have secondary unintended consequences. The key is using ice melting salts responsibly, and judiciously. Let’s find the proper balance between safety and environmental stewardship.
*2003. Costello, L et al. Abiotic Disorders of Landscape Plants: A Diagnostic Guide. Univ of CA Agriculture and Natural Resources Publication 3420