From The Ground Up: Protect your trees, shrubs from winter harsh salt damage

De-icing salts are one of the necessities of winter in Iowa.

De-icing compounds, such as NaCl, CaCl2, KCl and MgCl2, can damage landscape plants, something we don't think about when clearing the ice and snow from our walkways. Salts affect plant growth in several ways. When high levels of salt are present in the soil, plants are unable to absorb sufficient water even though soil moisture is plentiful. Plants suffer a salt-induced water shortage termed 'physiological drought.” High levels of salt restrict the uptake of essential nutrients by plant roots. Excessive amounts of sodium and chloride ions in plant tissue are toxic to many plants. Soil structure is damaged by high levels of sodium. Salt deposited directly on plant foliage can cause plant tissue dehydration.

Q: What are symptoms of de-icing salt injury to trees and shrubs?

A: The symptoms of salt injury to deciduous trees and shrubs include stunted growth, marginal leaf scorch, early fall coloration, and twig dieback. Accumulation of salt in the soil over several years may result in progressive decline and eventual death.

Salt damage to evergreens results in yellowing or browning of needles and twig dieback. Evergreens near heavily salted roadways often are damaged by salt spray. Spray damage is most severe on the side nearest the highway.

Q: How can I prevent damage to trees and shrubs from de-icing salts?

A: Homeowners can minimize salt damage by using de-icing salts prudently. Before applying salt, wait until precipitation has ended and remove as much of ice and snow as possible. Use de-icing salts at rates sufficient to loosen ice and snow from driveways and sidewalks, then remove loosened ice and snow with a shovel. (De-icing salts need to be applied at higher rates to completely melt ice and snow.) Mix salt with abrasive materials, such as sand or Kitty Litter.

Fifty pounds of sand mixed with one pound of salt works effectively. Avoid piling salt-laden snow and ice around trees and shrubs. While the amount of salt applied to major roadways cannot be controlled, steps can be taken to minimize damage. As soon as the ground thaws in early spring, heavily water areas where salt accumulates over winter.

A thorough soaking should help flush salt from the root zone of plants. If possible, alter the drainage pattern so winter runoff drains away from ornamental plants. When planting trees near major streets or highways, select salt tolerant tree species like bur oak, northern red oak, honeylocust, northern catalpa, Kentucky coffee tree, horse chestnut and eastern red-cedar.

For gardening questions, call Linn County Master Gardener hotline at (319) 447-0647.