Popular ice-melting salts—common table salt, calcium chloride, ammonium nitrate and urea—can damage plants, making them grow slowly, become deformed, succumb to disease, or die.
Treating for salt damage to plants
After exposure to salt spray, evergreens may show immediate effects, while deciduous plants (trees that drop their leaves in fall) may not show damage until the next growing season. Symptoms include yellowing or dwarfing of foliage, or dieback and “witches broom” of twigs. Damage is usually more noticeable on the side facing the drift.
If possible, treat by pruning dead or deformed branches and by washing away any surface salt residues. Treat for soil contamination if exposure has been long and heavy.
To alleviate the adverse effects of salt in the soil, apply gypsum as a corrective or preventive measure. Rate of application will depend on the severity of salt contamination. For moderately contaminated soil, or where it is anticipated, apply 100 to 200 pounds of gypsum per thousand square feet over the affected area. This treatment can be made every three years. For heavily contaminated soil, apply up to 700 pounds of gypsum per thousand square feet, or 150 to 200 pounds per year for up to three years.
Powdered gypsum should be used to promote its solubility and movement into the soil. Gypsum is a naturally occurring substance that will not pollute the environment. It is frequently used as a soil conditioner or for clearing muddy water in ponds and is available at garden centers in 50 pound bags.
Plants that have been weakened by heavy or chronic exposure to salt may not respond to gypsum treatment.
Protect at-risk plants and apply ice melters sparingly
1. Remove ice by mechanical means if practical.
2. Create drainage channels or barriers around plants where ice melters are used.
3. Use only the amount of ice melting chemical needed to do the job. Practice moderation.
4. Use dark-colored abrasives as an alternate or supplement to chemicals.
5. Use calcium chloride rather than sodium chloride when fertilizers are not practical.
6. Apply gypsum if sodium chloride contamination is anticipated.
7. Be especially careful in applying salts in late winter or early spring or when the ground is not frozen.