Posted: December 21, 2023

Once winter settles into Massachusetts, you know it’s only a matter of time before snow falls and ice crystals form on all your outdoor surfaces – from driveways to walkways to your car when it’s parked outside.

And what’s the best way to manage ice and keep it from forming in areas where you’d like to prevent skating to your vehicles or slipping and falling on the hard concrete? Add some salt.

While rock salt can be helpful for keeping you from turning your driveway into an ice skating rink, it can leave your trees vulnerable to salt damage.

Let’s answer the question, “What are signs of salt damage in trees?” so you can recognize when salt may be impacting your plants and talk about how to protect trees from rock salt during winter.

What Does Salt Damage Look Like In Trees?

Sure, salt can be pretty good at keeping roads and sidewalks clear of snow and ice, but it brings with it some side effects – the most visible ones being damage to trees. These signs will vary based on the type of tree you have. Some common salt damage symptoms include:

For evergreens, needles may turn pale green or yellow.

For deciduous trees, signs are tougher to spot but may involve:

  • Crusty dry soil
  • Bark discoloration
  • Yellowing leaves
  • Canopy dieback

You might be asking yourself, “If my trees are damaged by salt, when will I see symptoms?” These signs are usually visible in late winter for evergreens and early spring for deciduous trees.

If Salt Is Harmful To Plants, Why Do We Use It?

Part of how to protect trees from rock salt during winter involves understanding what rock salt is and how it works.

Rock salt is sodium chloride, which is a commonly used salt on roads. It's gritty, creating that instant grippable surface, and is effective at melting ice down to 20-degree (Fahrenheit) temperatures. Rock salt is usually easily available and the least inexpensive deicing option, as well as a pet-safe choice.

Since it’s the most affordable option for melting snow and ice, it’s a balancing act when using it near your plants. Rock salt has always had the ability to change the pH of soil, impacting plants that can’t take that elevation in salinity. This is, of course, only in reference to plants that don’t naturally grow on the coast and haven’t developed a tolerance for saltier conditions.

How To Protect Trees From Rock Salt Damage

Now that you know what salt damage looks like, let’s review some tips to avoid winter salt damage to trees and shrubs.

  1. Consider your salt options. Consider using a sodium chloride alternative, such as calcium chloride, potassium chloride, or calcium magnesium acetate, which can be less harmful to plants than sodium chloride.
  2. Rinse tree trunks with fresh water when the snow and ice clears to get rid of excess salt on or near the trunk.
  3. Irrigate the soil around the tree thoroughly with 1 inch of fresh water for the first 2 to 3 months of spring to flush out any remaining excessive salt.
  4. Before using salt and before winter arrives in late fall, spread gypsum on the soil in late fall. You can also incorporate biochar and compost into the soil to help with salt resilience.
  5. In spring, you can hire an Massachusetts Certified Arborist to remediate lingering salt issues with liquid humates and gypsum.
  6. Plant salt-tolerant trees, such as Eastern red cedar, Mugo pine, Southern magnolia, longleaf pine, yellow birch, thornless honeylocust, Kentucky coffeetree, black walnut, sweet gum, white spruce, and Colorado blue spruce. Healthy, well-maintained trees will always stand up stronger to winter weather and salt damage than stressed trees.

Salt Alternatives For Deicing In Massachusetts

Let’s look at the types of salts you can use to melt ice so you can understand the differences between them and gain more bits of knowledge concerning how to protect plants from salt damage.

Rock salt, as we discussed above, is sodium chloride. It can be harmful to trees if used improperly or excessively near plant beds, and it can also be corrosive to concrete surfaces.

In Massachusetts, we have some alternatives you can use.

  • Potassium chloride can melt ice down to 12 degrees Fahrenheit, but can be more expensive than sodium chloride. Mixing the two can help you get the best ice melting and plant protection benefits, while also saving some money in the process.
  • Calcium magnesium acetate is effective at lower temperatures than rock salt – down to -20 degrees Fahrenheit, and it’s less corrosive to grass, plants, and trees. This product stops snow particles from sticking together and lowers the risk of refreezing, which is different from sodium chloride and potassium chloride, which both form brines to melt ice. However, like potassium chloride, calcium magnesium acetate is also more expensive than rock salt.

At Hartney Greymont, we have both ISA and Massachusetts certified arborists located in Needham, Concord, Danvers, Cape Cod, and the surrounding areas. Give us a call to help prepare your trees for this winter season.

If You See Any Salt Damage Symptoms Or Need Help Preparing Your Trees For Winter, Call Your Hartney Arborist Right Away.

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