During the recent cold snaps, many thousands of tonnes of salt have been used to treat roads and pavements.
Of course, ensuring roads and pavements are not slippery is essential, but excessive use of salt causes environmental harm to trees, plants and animals.
Sodium chloride (rock salt) is the most widely used treatment for de-icing, but it does have some side-effects.
If used over long periods of time it can damage the metal on cars and eat up concrete and asphalt surfaces, so just imagine what it can do to your plants.
Unfortunately, the wind-driven salt spray from lorries and cars can travel up to 50 metres; trees and plants closest to main roads that have been regularly salted are most likely to be affected.
Salt it’s usually found in small quantities in the soil, but in large quantities it stops the grass from absorbing nutrients such as phosphorous and potassium as it can dehydrate the roots of the grass in your lawn.
If it touches the grass blades it can cause brown burns that reduce their ability to gain nutrients from the sun, and makes the plant more susceptible to the cold.
Salt also causes direct damage to plants and trees but this might not be apparent until months or even years after being contaminated.
The symptoms range from buds being slow to open to the browning of the leaf margins and in severe cases the defoliation of whole branches and tree death.
Road salt can also impact on the health of migratory birds. Birds can die from sodium poisoning or can suffer chronic effects especially if a source of freshwater is not available nearby.
Birds preening their feathers can ingest the salt crystals and as little as 4 grams of salt can be lethal to a bird; also, they may drink and bathe in water from salty puddles as paths and roads that have been treated are starting to melt.
If sodium crystallises on the feathers of birds it can destroy the feathers’ thermoregulatory and buoyancy functions causing the bird to die of hypothermia or from drowning.
How to treat it and limit the damage?
To avoid the salt reaching your plants, put partitions or objects to protect your garden. When scraping the snow and ice with your shovel, be sure you don't throw the snow and ice that contains salt onto any of the surrounding vegetation.
Use salt sparingly and mostly on paved surfaces that are not close to any kind of vegetation; use the smallest amount possible and apply only when necessary.
A handful of rock salt goes a long way—one handful per square metre; try mixing it with sand to reduce the amount needed. Sand has been used for decades, while it doesn't melt the ice, it does provide some traction on slippery surfaces; also, because it's natural, it won't contaminate soil and lead to landscaping problems. Cat litter has also been used in the same way as sand to boost traction, but it can make a mess, of course you don't want to track it into the house.
Rock salt is limited by temperature and it would only work at temperatures just below freezing; if the weather is colder, it becomes ineffective.
There are various alternatives to rock salts such as calcium chloride and magnesium chloride that work best in very cold temperatures and are safer for the environment.
Magnesium chloride is typically considered to be safer for use around plants and concrete surfaces than other products, while Calcium chloride penetrates ice quicker at lower temperatures.
Calcium magnesium acetate is the most environmentally safe product to remove ice. It won't corrode metals or cause harm to plant life; it can be effective against ice down to around -30°C.
Liquid de-icers are beneficial as they allow you to use less of the chemical and cover a greater area; however, they are often more expensive.
Water can be your best friend when fighting salt damage, especially if you live near the coast. The salt stays in the soil, so new grass won't thrive until you take steps to fix the salt content.
As soon as you suspect salt damage; water the area deeply, soaking it for several hours; continue watering every day for the next three to four days; this leaches the salt out of the soil, washing it down and away from where it can no longer affect your lawn or your plants and trees.
There is limited scope for treatment once a tree displays symptoms, but high levels of rainfall or watering between now and spring will help to leach the salt from the soil before new growth starts.