Help Minimize Salt Injury to Shade Trees

Each winter, thousands of tons of salt are applied to state and municipal highways in Illinois to combat snow and ice. While the procedure helps provide dry, safe highways, it also contributes to injury and death of trees along those roads and in town.

The injury occurs when salts are deposited by spray or drift on dormant stems and buds of deciduous trees and on stems, buds and needles of evergreens. The trees also are injured when excessive amounts of salts leach into the root zones.

The salt, whether moved by the spray of passing traffic or into the soil, can cause tree disfigurement, reduce plant growth and cause plant death.

Spray salt damage is most evident along heavily traveled highways where high speed traffic deposits sprays of salt on plants, causing the tissue to dehydrate. Damage is most severe within 60 feet of the road, although it can extend to 150 feet.

In city areas, where traffic moves more slowly, the greatest threat is a build-up of soil salt and excess sodium and chloride in the tissue of trees and shrubs along city streets, driveways and sidewalks. Salt plowed and shoveled onto boulevards and lawns may also be absorbed by the roots, causing direct toxicity to the plants.

The damage means increased maintenance costs for pruning, fertilizing and extra care for damaged plants. While salt-tolerant species are available, it is hard to match them to soils best suited for them. There also is the increased risk of a single disease or insect destroying a lot of trees when a single species is used.

One way to avoid the damage is to avoid deicing salts, although this may not be feasible in rugged weather. The salts also could be diluted by mixing them with an abrasive such as sand, cinders or ash. Their application could be limited to high-risk areas such as intersections, hills, steps and walkways. Calcium chloride deicing salts could be used instead of sodium chloride.

Susceptible plants could be protected by constructing physical barriers of plastic, burlap, plywood or window screen on or in front of them. Shade and ornamental trees could also be planted away from the spray drift zone or areas where salt laden snow will be deposited, if there is room.

Winter 1998
Time to Think Christmas Trees | Caring for Poinsettias & Christmas Trees | Constructing a Holiday Wreath | Help Minimize Salt Injury to Shade Trees | '99 All-America Selection Vegetable Winners | Bug Bites | Cybergarden Sites | Lawn Care Calendar | Hort Shorts | Hort Tips | Locally Grown—Pumpkins & Winter Squash | Food for Thought | Food Handling | Food Safety | Health & Household Tips | Did You Know?

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