Road salt damage to garden and landscape plants is a problem for many gardeners. Runoff from the road contains dissolved salts that not only directly injure the plants but also can change the structure of the soil, causing it to become compacted, thereby restricting the nutrients, water, and oxygen available to the plants.
Although the salt is applied throughout the winter, most salt damage occurs in late winter and early spring when plants are beginning active growth. Growing portions of the plant, such as shoot tips and young leaves are affected the most. One of the symptoms of salt damage is marginal scorch, a dried burnt effect on leaf edges. If you have plants near a possible source of excessive salt, bring a soil sample to your county extension office and request a soluble salts test to determine if you have a problem.
The battle against salt damage continues year round:
During the winter
The goal is to prevent salt from reaching the plants, and to wash it off the plants that it does reach.
Do not pile snow containing salt around plants or trees or put it where runoff will flow over plant root zones.
Ask the road maintenance people if there is anything they can do to direct salty runoff away from your property. Where runoff is unavoidable, flush the area around the plants in early spring by applying 2 inches of water over a 2-3 hour period and repeating this three days later. This will leach much of the salt from the soil. If salt spray from the road surface is a problem, use copious amounts of water to rinse the foliage and branches of any affected plants when salt spray is heavy and again in early spring.
During the summer
Work to improve planting conditions. Incorporate large quantities of organic materials into salt damaged soil to enhance its texture and to increase its water and nutrient holding capacity. Plants that are already stressed by salt will do much better if no other stresses are added to them, so be sure that you properly fertilize, water, and otherwise care for them.
When selecting species for a new roadside planting, minimize the potential for salt damage by planting salt tolerant species such as white oak, honey locust, Scotch pine, red oak, junipers, roses or asparagus. Avoid salt sensitive plants such as red pine, white pine, black walnut, red maple, and sugar maple. A low wall or a hedge of salt tolerant evergreens can deflect salt spray from sensitive plants nearby.
Remember the damage that salt can cause when removing ice from home walks and driveways. Instead of tossing a handful of rock salt on slick surfaces, stick with sand or sawdust to improve traction on slippery sidewalks.
Diane Relf is a retired extension specialist in horticulture, and Bonnie Appleton is an extension specialist in horticulture with the Virginia Cooperative Extension. This article is an excerpt of a longer one written via the Virginia Cooperative Extension, Virginia Tech, and Virginia State University at http://www.ext.vt.edu.