Salt damage to landscape trees and shrubs
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
As our landscapes slowly wake up from their winter slumber, we’ve been getting quite a few reports of plants suffering from apparent salt damage. Many parts of the state had record or near-record snowfall totals, which means road crews applied record or near-record amounts of de-icing salts. Where we live in Mid-Michigan most of our snow came in 2-4 inch increments, which meant the salt trucks were out like Chicago voters, early and often. This constant bombardment with sodium chloride can take a toll on a lot of landscape plants. Common signs of salt damage are scorched needles on conifers, especially on the side of the plants facing the road, witches brooms (clusters of irregular growth at the end of terminal shoots) and crown or branch die-back.
Dealing with winter injury
As with many environmental injuries, there is typically not a lot that can be done about salt injury after the fact except to keep the patient quite and comfortable and let nature take its course. For evergreen conifers, the initial damage, especially right about now, often looks worse than the final outcome. Needles can experience pretty heavy scorching, but as long as the buds are not damaged and the plants flush normally this spring, they will usually be OK. Branch die-back in deciduous trees and shrubs can be more problematic and may require some attention. Right now, we’re in a “wait and see” mode. As trees and shrubs begin to leaf out, salt damage or winter freezing injury will become apparent. Play close attention to recently planted (within the last year or so) trees and shrubs, which are often prone to die-back. Also bear in mind that salt exposure varies depending on type of road (four lane arterial road versus two lane county road); exposure (prevailing winter winds are from the north and west so trees on the east and south sides of road often receive a heavier salt load); and traffic speed and volume (increased traffic speed increases the distance salt spray will travel).
Road salt is a fact of wintertime in Michigan. Many road commissions have adapted strategies to optimize salt effectiveness and incorporate alternative de-icers into their snow and ice management. But the fact remains sodium chloride is the lowest cost option to for road deicing. As I’ve noted before, the best solution for long term management of salt damage is selection and protection. In salt-prone areas, select plants that are tolerant of salt exposure and where possible, use physical barriers such as burlap screens to prevent salt spray from reaching sensitive plants.