During a cold, snowy winter, deicing salts help keep sidewalks, roads and highways clear and improve safety when walking and driving. Unfortunately, deicing salts leach into soils and are splashed onto plants by passing cars, where they can build up and often cause harm to plants. Even a light covering of salt on a large driveway can build up in nearby soils, as it mixes with snow which is then piled up on adjacent garden areas.
How to recognize salt damage:
Because excess salt in soils inhibits plants' ability to draw up water, salt damage can sometimes resemble drought damage. A strip of dead grass right next to a sidewalk or driveway that had salt applied to it is a sure sign of salt damage. Large, established plants in areas where salt has built up in the soil may show little or no signs of damage, but newly planted seeds are likely to have very poor germination and growth. Established plants that are splashed by salt spray can be recognized by stunted, twisted growth, and leaves that turn brown around the edges. Another clear indicator that damage is caused by salt spray is when the damage is clearly only on the side facing the road, where the salty spray comes from.
How to treat salt damage:
If you suspect your plants have been exposed to salt spray, wash the plants with fresh water when the temperature rises above freezing. Soils that have had salts leach into them should be watered deeply several times in the spring to dilute the effects of the salt.
How to avoid salt damage:
To avoid the damage caused by salt around your home, you can simply reduce the amount of deicing salts used on your property. When conditions are extremely icy, sparingly applied salts are unlikely to cause any damage if they are only used once or twice in a winter. For more frequent use, sand can be applied to icy sidewalks, and here in Edmonton, it is usually available for free at your nearest community centre. Kitty litter is also supposed to be quite effective at reducing icy conditions. If you wish to use an ice melter, a product with CMA (calcium magnesium acetate) will be effective in melting ice and should not damage plants, although it is generally more expensive than the chloride-based products. On the small scale required by most homeowners, however, the increased cost may be offset by the the savings of not having to replace plants regularly.
If the salt damage you are trying to avoid is out of your control because a neighbour or city crew is applying the salt, your options are mostly limited to planting salt-resistant plants. Some examples of salt-resistant trees are cottonwood poplars, honeylocust, Jack pine, Austrian pine, white spruce, Colorado spruce, bur oak, red oak, green ash, white ash and Russian olive. Some shrubs that might be successful are mugo pine, junipers, rugosa and scotch roses, caragana, saltbush, shrubby cinquefoil, Japanese spirea, lilac, alpine currant, arrowwood and European cranberrybush. When selecting perennials for salt tolerance, ones known to be drought tolerant will often have the most success. Some that are known to tolerate salt conditions are lady's mantle, sea thrift, 'Karl Foerster' feather reed grass, amethyst sea holly, blanket flower, blue lyme grass, wooly thyme, perennial flax and yarrow.