Rock salt can damage your lawn, flower beds
Q. How damaging to plants and lawns is sodium chloride that is used to melt ice on walkways?
A. Sodium chloride, or rock salt, is the most commonly used de-icing product because it is cheap and readily available, but it is also the most damaging to plants. When you see areas of dieback on a plant, such as browned leaves or needles and dead twigs and buds, especially if the dieback faces a driveway or road where sodium chloride was used, that is the likely cause.
The damage can be hidden in deciduous plants until spring when plants emerge from dormancy. Evergreens will show damage more quickly in the spring with yellow and browning tips. There are various ways in which rock salt can impact your garden plants and the soil that sustains them.
Salt spray, which occurs as vehicles drive down either a driveway or street, lands on stems, buds, branches or needles. When this happens, plant tissue burns and desiccates, or dries out, leaving plants vulnerable to the damage of winter cold and wind. If this happens in March or later it can kill buds, which destroys flowers and leaves for the spring growing season.
Salt water runoff, which occurs when salted areas melt, including when salt in plowed snow is deposited on lawns and near plants, can be detrimental because the salted water ends up in soil. Sodium and chloride ions separate once they mix with water. Chloride becomes available to be taken up by the roots of plants into their tissues traveling up to their leaves. Large amounts of chloride can interfere with the uptake of nutrients from the soil such as potassium and phosphorus that plants need to be healthy. This causes damage and sometimes death of an overexposed plant. Too much chloride can cause stunted growth, leaf burn or leaf die-back.
High sodium in soil can cause water to move from plant roots to the soil, causing root dehydration. Compaction can occur when too much sodium gets into the soil because of the displacement of other soil nutrients by the sodium in water. This decreases drainage, which means plants can't get air or water from the soil, leading to a lack of nutrients and death.
To mitigate problems with rock salt, you can target only the areas that are specifically in need of de-icing. Consider salt water runoff before you apply, and don't shovel that same area off into a garden. You can water heavily in areas where well-drained soils have been exposed to sodium chloride to flush out the sodium. In poorly drained soils that will not work. You will have to add organic matter to improve the soil structure so be careful not to use salt around soils that are not well-drained.
Alternatives to sodium chloride, such as sand, sawdust or ash, are better to use in areas near lawns and gardens. Other de-icing products include calcium chloride, magnesium chloride, potassium chloride or calcium magnesium acetate, which, while more expensive than rock salt, are safer around plants.
You can also put up barriers, such as burlap, wood or plastic wrapped around or in front of hedges, trees or other garden plants to prevent the salt spray from reaching the plants. Another option is to plant salt-tolerant species. For example, juniper (juniper spp.), Northern Red Oak (quercus rubra) and sumac (rhus spp.), in areas near roads, driveways and walkways where salt will be used. While there are salt-tolerant species, remember that no plant is immune from damage if conditions deteriorate because of excessive salt exposure.
- Nancy Degnan
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.