SHUC and Uncover have tried very hard to make Forbes Avenue look like Rodeo Drive, or name any tree lined street that is attractive to shoppers. (Murray Avenue is a future project with Councilman O’Connor’s help.) Research is long term and clear that people spend more and linger longer on attractive tree lined streets.  It is therefore in our best interest to keep the trees we have healthy and looking good.  This means watering during drought.  And in winter, when icy sidewalks pose a problem for retailers and restaurants, we need to treat our sidewalks – but keep the health of our street trees in mind. 

We hope you will read this and purchase de-icers that are “tree friendlier” and also pet friendlier. The increased cost is worth it long term.

Rock salt is the most common form of ice melt used today, and the cheapest, but also the most damaging.

Most ice melts are blends of the same ingredients: sodium chloride, calcium chloride, or magnesium chloride. (See ingredient chart below.)

Rock Salt is highly toxic to trees. When too much salt is applied, it can build up in the soil and start to desiccate (make extremely dry) and destroy tree roots. (You can see this in the spring in a few ways: either when a tree leafs out and the edges of the leaves have brown margins, or when the tree fails to leaf out at all because it died from too much salt.

Not only will salt hurt the trees, but over time too much salt can begin to destroy soil structure which can create soils where nothing will grow. Salt spray from fast-moving traffic can also land on branches and buds, causing desiccation and damage. Each tree species has a different level of tolerance to salt. While safe salt for trees does not exist, there are a number of things that can be done to protect trees if salt is used:

  1. Plant the right tree in the right place, if it’s a street tree some species are more salt-tolerant than others. Ask an expert about the salt tolerance before choosing your tree.
  2. Clear as much snow and ice as possible before salting, and use it conservatively.
  3. After thawing, sweep up any remaining salt and save it to re-use later.
  4. When spring arrives, water trees that have been exposed to a lot of salt. This will help to wash the salt from the soil.
  5. Consider an ice melt alternative.

Just remember, there is no safe salt for trees!  No matter what product you use, remember to use it conservatively!

Rock Salt is also a Danger to Pets.  This is because salt can seep into the paws and the fur. During high temperatures, the salt can burn the skin surface, causing redness and skin ulcers, which may ultimately lead to bacterial infections. Exposure to excessive salt, often through licking salt off their paws, can also trigger intestinal problems and stomach inflammation.  For cats, licking salt can lead to gastrointestinal distress.  Vets recommend that you lead pets through a “rinse tray” after a walk and suggests a water-filled pan at the entry to your home, with a towel nearby.

Here is the science behind Rock Salt damage to concrete.  Salt damage to concrete mainly occurs due to chemicals that react with the surface of the pavement. These structures are generally made with white-gray concrete. The calcium hydroxide present in concrete reacts with the calcium chloride in Rock Salt, creating calcium oxychloride (CAOXY) in salt, thus wreaking havoc. When forming inside concrete, CAOXY crystals expand, causing internal cracks and crumbling. This leads to increased salt damage to pavements – which is further amplified by the effect of the freeze-thaw cycle.  Salt also lowers the freezing point of water and increases the pressure of frozen water which intensifies the effect of the freeze-thaw cycle.

Let’s Consider the Trees and Ice Melt Alternatives to Rock Salt. 

When you apply any De-Icer: Lay it in layers. Always use a gentle hand when applying any type of ice melt to concrete. If you can, lay down a thin layer before a storm, then another light layer during the storm. As the snow falls, the salt goes into solution and makes it easier to shovel or otherwise clear away the snow and ice. It’s not fairy dust that you can sprinkle on top of snow and have it magically disappear. (Recommendation from Consumer Reports)

When purchasing de-icing materials, no matter what brand, be aware of the ingredients which will be listed usually on the front of the bag.  Also, note the benefits that are associated with each ingredient. Choose as if the life of your tree, pavement, pet – depends on it!

Some Home Depot Choices

Avoid: Ice Away “Rock Salt” is tough on trees, pets and cement.  

Safe Step is more Pet Friendly

Magnesium chloride & sulfate of potash

Safe Step 4300 Will not harm trees if used as directed.

 Safe Step 7300 Calcium Chloride use as directed to avoid harm to trees.           

Note: Thanks to Tree Pittsburgh and the Western PA Conservancy TreeVitalize Project for providing information for this article.