Welcome to Michigan winter. It took a while to get here, but we have a good amount of snow and ice now, which means people break out the salt to make walking and driving safe.
You may have heard that salt is bad for plants, but do you know why, and what to do about it? The first thing to know is that there are two ways salt can impact your landscaping, whether it be your lawn, trees or shrubs near walks or roads. One is salt spray, when salty snow or water is splashed on the foliage and buds of a plant. Since deciduous trees lose their leaves, it is mainly their buds that are impacted by dessicating (drying out) the bud scales plants, damaging the developing leaves and flowers.
Evergreens especially suffer from spray damage when they are near roads or sidewalks where spray occurs because their needles provide a lot of surface area to capture the salty spray (the image shows pine trees that have salt damage on the side that faces the salt spray). You may not see the damage until late winter or spring as it takes a while to impact the plant.
The other salt impact is in the soil. As the snow melts or rains fall the salt that has been sprayed or spread onto the soil is dissolved and seeps into the ground where the roots are. If sodium chloride salt is used (rock salt), the sodium and chloride ions, which plants don’t use, displace the potassium and phosphorous nutrients that the plants do need. When the plants move the fluid up to the leaves, it takes along the salt and sodium too, and those inhibit the photosynthesis and chlorophyll production. If it is in high enough levels, chloride can reach toxic levels, causing leaf burn (see the photo of the aspen leaves) or death.
So, what can you do to protect your plants and lawn? First, know that it’s not too late to take action as late winter salt applications cause more damage to the roots because there is less water to flush it out of the root zone.
So, here is what you can do:
Protect your plants by placing physical barriers such as burlap, plastic or wood between the spray source and your plants
Use less salt by combining it with sand or sawdust Use non sodium chloride salt products (calcium chloride, magnesium chloride, potassium chloride or calcium magnesium acetate (CMA), or just sand Be careful when you put down a salt product so you don’t cast it onto your plants or the soil below them Avoid planting salt sensitive plants in areas where runoff from driveways and sidewalks go If you have porous soil (most of Novi’s isn’t), watering heavily when the ground thaws may help dilute the salt.
SALT TOLERANT PLANTS:
Use plants that are known to be more tolerant of salt in areas near salt spray or runoff locations. This isn’t a guarantee because heavy salt concentrations can kill even salt tolerant plants, but it gives them a fighting chance.
Below are some websites that list plants with and without salt tolerance. https://www.canr.msu.edu/news/selection_of_salt_tolerant_trees https://pdf.countyofdane.com/myfairlakes/A3877.pdf
The bottom line is that rock salt is not good for any plant, so do what you can to prepare your landscape for it, and do what you can to minimize your own salt intake.