GardenWise: Considering the potential harm of winter’s ice-melting salt to our landscape plants

The cliché “out of sight, out of mind” seems to apply to us now, as our “sleeping” plants may literally be hidden under a blanket of snow. While Old Man Winter is encouraging a couple of months of plant dormancy, the ravages of his cold weather may cause after-effects of poor plant health. These plants should definitely not be out of mind during our winter weather.

The application of salt to our highways, driveways and sidewalks may be creating a problem now for your plants when they awaken in the spring.

We often think of salt damage only as it relates to our cars and trucks. Our local highway departments are busy spreading salt on our streets to make travel safer. As a home gardener, you may also use salt crystals on your driveways and walkways for greater traction and safety.

While salt creates a safer situation for our vehicle and foot traffic, it produces a problem for the plants that receive a blast of salt-laden snow and ice from snowplows or a salt-spray from moving cars, snow throwers or our shoveling a path.

Sodium chloride becomes toxic to plants when dissolved in water. This is a problem on two fronts: saltwater spray on the branches and trunks and accumulation in the soil surrounding the roots.

Think about how table salt in a shaker tends to clump as it absorbs water. Preserving food with salt illustrates the same principle.

Salt mist sprayed by cars or plows can coat a plant’s surfaces and immediately begins to dry. Plants soon lose their cold hardiness and may be killed by super freezing. Add the salt mist to the normally-dry winter weather with strong winds and disastrous results will probably occur.

Within just a few months, you will notice salt spray damage on the side of the plant that faces the road or sidewalk. Evergreens may even show this effect later in the winter, with needles’ becoming brown at the tips. On deciduous trees and shrubs, the salt damage may show up later in the spring, when the buds facing the road are dead or very slow to break open.

Salt damage doesn’t stop with just the misting to the upper plant; the salty solution will eventually enter the ground and saturate the soil surrounding the plant’s roots.

Sodium chloride breaks down into sodium and chlorine. Sodium prevents the intake of the much-needed phosphorous and potassium, while the chlorine is absorbed into the plant system. The salt solution in the soil locks up water in the soil and keeps it from entering the plant tissue in the roots. While it may have an adequate amount of water, the plant will suffer from drought-like conditions with little moisture available. The chlorine accumulates in the leaves, interferes with photosynthesis and soon turns the plant leaves yellow. This is often referred to as “leaf scorch.”

Either type of damage, salt spray to the upper plant or salt-laden soil, could be deadly to a plant if the condition occurs for several years, or shorter, if the plant is already susceptible to this type of damage.

There are several precautions you can take to prevent salt from damaging plants.

- Screens of fencing or burlap may be erected to ward off salt spray from nearby roads.

- On your walkways, try to reduce or eliminate the application of salt near pathway border gardens. Consider using calcium chloride, kitty litter granules, sawdust, sand or even a granular chemical fertilizer (e.g.,10-10-10) for greater traction.

- As you eventually clear your pathway with a shovel or snow thrower, do not pile the salt-laden snow around plants or in places where melt-off will drain into plant areas.

- During a thaw, try to divert the salty melt-off water away from plants, if possible.

- In the spring, plan to flush the area around the roots exposed to winter salt with fresh water, which will leach away much of the salt from the root soil. As the plant growth increases during March and April with greater warmth and light, the presence of salt is especially serious if not washed away.

-As you work in your gardens next season, analyze beds that are near salt-use roadways and walkways and improve the drainage.

As you design (or re-design) garden and landscape areas, try to consider not only the size and appearance of your plants, but also the level of plants’ salt tolerance if the planting is to be near a salt-use area.

Below is a listing of a few plants and their salt tolerances. This listing represents some of the references from Cooperative Extension Services from Cornell University, Colorado State University and the University of Wyoming.

Salt resistant trees include white spruce, Austrian pine, black/honey locust, sycamore, white/red/black oak and willow; moderately salt tolerant are ash, poplar, birch, cherry and red cedar.

Salt resistant shrubs are juniper, bayberry, firethorn, native honeysuckle, forsythia, sumac, privet and some plum varieties.

Salt resistant grass varieties include big blue stem, little blue stem, creeping bentgrass, Bermuda grass, many fescues and perennial ryegrass.

Try to control the use of snow and ice melting salt solutions in and around plants throughout the winter season. Be especially diligent when the temperatures start to warm throughout the next few months and plants break out of their dormancy. Plants will then actively absorb nutrients and water and the toxic salt solution will be the most deadly. Heads up in the winter will mean greener, healthier, and living plants in future seasons.

Direct gardening questions to me via the “Springville Journal.”
Leo Lubke is a Master Gardener and a member of the Garden Writers Association.

Seasonal gardening tip:Carefully place shoveled snow over perennials. Do not use snow that has salt in it! Snow will insulate the plants from cold temperatures. The temperature below the snow increases by 2 degrees for each inch of accumulation.