Salt Injury in Landscapes

As the weather begins to warm up and our landscapes begin to show new life, we occasionally receive phone calls from homeowners and landscape professionals about plants that are exhibiting injury symptoms. These symptoms can range from minor yellowing of foliage even to death of plants. While a number of factors can cause this, a common one is injury from deicing salts.

Salt injury is generally limited to areas adjacent to an area that has received deicing salt applications during the winter, such as along roads, sidewalks, or patios. Salts that come in contact with foliage can cause burning and discoloration of the foliage. This type of injury can be significant depending on the percentage of the foliage affected, but the injury will generally subside once the foliage is rinsed by rainfall or irrigation. However, if high levels of salt enter the soil, they can continue to cause damage.

 When salts enter the soil, they can change the way that water moves within the soil and cause the plants to be stressed by restricting the ability of roots to take up water from the soil, in essence causing water stresses similar to drought stress. These salts can also displace essential plant nutrients, leading to possible nutrient deficiencies within the plant.

However, not all landscape injuries that we observe in the spring are salt damage. Winter can be brutal on landscaping plants in other ways. Cold temperatures, extremely dry air and strong winds can cause many plants, especially evergreen trees and shrubs, to lose moisture rapidly, leading to browning of foliage. This type of injury, known as desiccation injury, may closely resemble salt injury, but can be found in plants away from deicing salt applications.

If salt injury is suspected, it is recommended that the soil be tested for soluble salts and sodium (Na), in addition to a routine soil test, to determine if salt levels are high enough to cause further injury to plants. By analyzing for these properties, you can assess the amount of impact that the deicing salt has had within the soil profile and take steps to mitigate its effects.

Correcting mild to moderate salt injury generally involves flushing the excess salt from the rooting zone. This requires thorough and repeated watering to cause the water to flow through the rooting zone, thereby reducing the potential for toxicity. This should be done as soon as possible to reduce further injury. In situations of very high salts or poor drainage it may be more practical to remove and replace the affected soil.