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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis

Salt Injury from Martha Smith

Posted by John Fulton -

How exactly does salt damage plant material? Anyone who has tried to get table salt out of a wet salt shaker knows that salt readily absorbs water. Rock salt exhibits the same property in the soil. That is, it absorbs much of the water that would normally be available to roots. Even though there is adequate soil moisture, high amounts of salt can result in a drought-like environment for plants. Plants will exhibit drought or root damage injuries.

When salt dissolves in water, the ions separate and plants absorb the chloride ions. They accumulate in the growing points and build up to toxic levels. Stunted yellow foliage, premature fall coloration, leaf scorch and twig dieback are common. Excessive sodium in the soil also obstructs the availability of important nutrients. However, many of these symptoms occur after bud-break in the spring and well into the growing season. It is often difficult to connect early fall color to the previous winter's salt applications.

When salt is sprayed on plants from passing cars, injury occurs in cells and tissues sensitive to the chloride ion. Chloride ions move in the transpiration stream to the leaf tips and margins and again accumulate to toxic proportions. Usually this damage is on the side of the plant facing the road, and to plants located downwind. Often the plant will grow out of the damage, with new growth covering injured areas. On evergreens, pale green, yellow or brown foliage may be evident in late winter into spring if salt damage has occurred. On deciduous plants, death of buds and twig tips, especially apparent during the spring as buds begin to open, indicates that spray damage has occurred.

How can you avoid salt damage this winter? The obvious answer is to reduce the amount of salt used. Limit applications to high risk locations such as walkways and driveways on an incline, steps, and areas where water accumulates only to refreeze again and again. Avoid applying pure salt; instead mix salt with an abrasive material such as sand, ash or kitty litter.

When applying a de-icer, wait until you have finished shoveling or plowing. If possible, wait until after the threat of more snow has passed before spreading salt. This will help reduce the amount of salt draining from the pavement into the landscape.

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