Spring has arrived at last, but our trees and shrubs might still be impacted by the winter ice management methods used in our city.
Cities such as Toronto apply thousands of tons of salt to manage icy roads and sidewalks throughout the Canadian winter months. De-icing salt plays an essential role in ensuring the safety of our city’s streets and pathways. Although there are alternative solutions to salt, it remains cost-effective and easily accessible. Even if you don’t personally use de-icing salts on your property, residues from the city streets can still find their way into your yard and garden.
Salt in the soil will inhibit the ability of the plant to uptake water and nutrients. The cells of the root are essentially blocked by the presence of the salt and the plant cannot properly absorb what it needs from the soil. This will result in plant stress, similar to what happens during drought conditions. High concentrations of salt in the soil will actually be toxic to the plant.
In addition to causing problems underground, salt spray that contacts evergreen needles or dormant buds will dry out the plant tissue, making it prone to winter freezing injury.
Symptoms include:
- Browning or yellowing leaves and needles, especially on the road-facing side
- Premature defoliation or branch dieback
- The tips of branches may dry out and die, particularly those closest to the road or salt source
- Prolonged salt exposure can weaken the tree’s bark, making it susceptible to cracking or peeling
- A visible white crust may form on the tree where salt has settled and dried
- Trees may experience slower growth, reduced canopy density, and increased vulnerability to pests and diseases
The damage often intensifies in late winter when trees are most vulnerable.
Soil Contamination
Melted snow transports salt-infused water into the soil, which interferes with a tree’s hydration system. This leads to osmotic stress, compelling roots to exert extra effort to take in water—similar to trying to sip through a blocked straw. As time passes, the buildup of salt raises soil salinity, rendering it unsuitable for trees to flourish.
Long-term effects include; slow or stunted growth over time, disrupted nutrient intake leaving the tree malnourished, weak or dying roots, as well as heightened vulnerability to diseases and environmental stress. Healthy soil relies on beneficial microorganisms, which can be killed off or disrupted greatly by high salt concentrations. Salt alters soil pH, making it more acidic or alkaline depending on the salt, causing further stress. If one tree is affected by salt, chances are the surrounding plants are as well, creating a less hospitable ecosystem for the tree.
How to Prevent Salt Damage
- Use Salt Alternatives: Opt for less harmful de-icing materials such as sand, gravel, or kitty litter. These provide traction without the harmful effects of salt. If you still need to use salt, consider calcium magnesium acetate, which is less damaging to trees.
- Apply Salt Strategically: When using salt, apply it sparingly and only in areas where absolutely necessary. Avoid spreading it near the base of trees, shrubs, or other vegetation.
- Redirect Snow Piles: Avoid piling snow that contains salt near tree roots or planting beds. Instead, redirect it to less sensitive areas of your yard.
- Create Physical Barriers: Use burlap screens, snow fences, or other barriers to protect trees and shrubs from salt spray, especially if they are close to roads or walkways.
- Water Wisely: After winter, flush the soil around your trees with water to wash away accumulated salts. Use a slow, deep watering technique to ensure the salt is pushed below the root zone.
- Mulch Around Trees: Apply a thick layer of mulch around the base of trees to help retain soil moisture and buffer the root zone from salt exposure.
- Plant Salt-Tolerant Species: In areas prone to salt exposure, consider planting trees and shrubs known for their salt tolerance.
- Prune Proactively: Prune weak or dead branches before winter to reduce the risk of breakage and exposure to salt spray.
- Wash Off Salt Spray: On warmer winter days, rinse salt off branches, needles, or leaves with water. This prevents salt from accumulating and causing damage.
- Improve Soil Health: Enrich with organic matter and test its salinity levels regularly. Healthy soil helps trees resist the effects of salt exposure more effectively.
- Create a Buffer Zone: Plant trees and shrubs farther from roads or walkways where salt is regularly applied. This extra distance reduces exposure.
- Professional Arborist Solutions: An arborist can offer a variety of solutions to salt damage. Salt buffer treatments are an option in which the arborist will apply gypsum (calcium sulphate) in the late fall and early spring. This is a granular product applied to the surface of the root zone. The gypsum ions bind with the saly ions, making the salt highly soluble and flushing through the soil at a much faster rate. Antidessicants are another solution where an arborist sprays is applied to the foliage of evergreens in late fall and winter. This protective coating seals the leaf from damage. An Arborist can also apply a low salt fertilizer deep into the soil come spring to boost plant recovery, health and vigour.
If you think your trees and shrubs are suffering from winter salt damage, give your arborist a call. They can diagnose the problem and come up with solutions for your soil and trees this spring.