Road salt is very effective at clearing ice from roadways and walks, but plants bear the brunt of the leftovers. Once the salts dissolves, it infiltrates the soil, creating a salty mess.
In the photo below are two black walnuts situated at the end of a parking lot. You can see the snow piles at the base of each tree and the salt-coated parking lot. The customer called because there have been dead branches falling from the trees. I looked at the trees after all the leaves were off and thought it would be a straightforward canopy cleaning... remove a few dead branches for safety.
Once we climbed up into the trees it became clear that salt was slowing killing these trees. Most of the branches in the upper canopy had dead tips. The branch tip is where the most vigorous growth occurs, and they were dying off. The salt build up in the soil was actually preventing the tree from transporting water to the tips of the tree.
If you do a quick internet search, you will find the many ways that salt harm woody plants. The biggest reason is salt’s ability to prevent plants from absorbing or taking up water, also known as physiological drought. Salt spray along roadsides is another common form of salt damage. The spray coats the dormant buds and essentially burns them, killing the buds or slowing their growth.
When using salt on your property:
- Use salt sparingly and clean up large spills or piles.
- Mix some sand into your salt to “stretch” the salt out bit more.
- Avoid piling snow with lots of salt on the root zone of trees and shrubs.
- Protect valuable plants with physical barriers to keep salt off of foliage and out of root zone.
Resources for preventing salt damage or minimizing it:
• Plant salt tolerant varieties of trees and shrubs. This is really good!
• If you have a pile of salt-laden snow at the base of your tree or shrub that you want to protect, you can flush the soil out with water before bud-break once the ground has thawed. Basically you would have to flood the root zone to purge all the built-up salts present.
• Use only sand or familiarize yourself with an ice scraper. My dad can attest to my extensive use of this tool as a kid, so I could shoot hoops all winter outside.
There is a lot of good info on the web about salt and the damage it can inflict on plants and trees. This is a only a starter to get you thinking about it. Educate yourself and others on the consequences of salt, so as a community we can keep our canopy as healthy as possible.