Caring for Your Trees in Winter

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De-icing Salts and the Health of Your Trees

Even though we haven’t seen any significant snow in the Philadelphia area this winter, it’s important to keep in mind how we can protect our trees from the harsh conditions that winter brings. When we prepare for snow, we often turn to chemical salts for their snow and ice-melting capabilities, spreading them over the sidewalk and the street. But these chemicals can wreak havoc on the health of our trees as they leach into the soil.

If you have yard trees that border the sidewalk or street, try to create a physical barrier between them and the street (a small chicken wire snow fence will work). If you are the one spreading the salt, take into consideration some tree-friendly alternatives to the sodium chloride (“rock salt”).

Keep in mind that sand is the best product to use to avoid harming your trees. But if you need a little more melting power, here are the pros and cons of some rock salt alternatives:

• Calcium chloride – This salt is less harmful to trees than rock salt, comes in pellet form, and works below 0 degrees F. It can be a skin irritant, so always apply with gloves on. High concentrations can damage concrete.

• Potassium chloride – This salt presents no harm to vegetation, and is not a skin irritant. However, it is more expensive and harder to find. It only melts ice when the temperature is above 15 degrees F.

• Magnesium chloride – This salt works until -13 degrees F. It is less damaging to concrete, less toxic to plants, and less corrosive to metals than any other salt. It is correspondingly more expensive and harder to find.

Finally, you might try mixing sand or other gritty materials (cinders, ash, etc.) with salt in a ratio of salt:sand between 1:4 and 1:10.

Best of luck as you care for your trees this winter. You’re one in a million!

Erica Smith
Philadelphia Parks & Recreation