Tree Talk: Snow, salt and soils

Snow, salt and soil: Not a recipe for the latest trendy dish. But it could be a recipe for tragedy on your turf and trees.

As cold and snowy weather sets in many of us focus on safety precautions, as we should. We watch the weather forecast, we gauge the extra time it may take to travel, we check outside to see if we need to sweep or shovel the walk...and maybe, for good measure, we sprinkle (or pour) some de-icing salt on surfaces where ice has formed. Safety first. While safety must be a priority during every season, there can be unintended consequences of winter de-icing products on nearby turf and trees.

Above Ground: Salts that end up on plant surfaces will desiccate evergreen needles, damage that can appear soon after it occurs. On deciduous trees (those that lose their leaves in winter), salt deposition on buds from salt-spray can disfigure trees through twig and branch die-back, once spring growth is triggered. Symptoms on foliage may look like scorching on leaf margins. Affected turfgrass simply will look dead.

Below Ground: What we do not immediately see is the effects of de-icing products on soil, where salts accumulate from snow melt run-off or products that are swept off hard surfaces and then dissolve into nearby soil. Accumulated salts alter the chemistry and structure of the soil, home to a vast community of soil microorganisms ("good" bacteria & fungi), earthworms and other soil critters. These organisms are a vital component of healthy soil, since they aerate the soil and add organic matter. Healthy plants depend on healthy soil and healthy soil depends on these organisms, which cannot survive in a high-salt environment. As soil health is affected, so is the ability of plants to absorb water and nutrients from the soil. It may take a number of years but woody plant health can be seriously affected by things we do, even during the dormant season. Unintended consequences.

What can we do? The best thing we can do is employ Best Management Practices. First, use only as much de-icing product as necessary. More salt is not better (doctors have been telling us this for years!) when it comes to the surrounding soil and the plants supported by the soil. Consider mixing salts with alternative materials such as kitty litter or sand, which won't melt snow but will provide traction.

Diluting the salt product will cut costs, too. While turfgrass may be relatively easy to replace, trees are not. Trees that are more tolerant to de-icing salts include amur maple, thornless honeylocust, chokecherry, cottonwood, bur oak and Japanese tree lilac. However, years of continuous use or over-use of product will alter soils to the point that even these tough trees will suffer.

The benefits of trees are worth the investment and trees deserve our care. Healthy trees contribute to healthy communities, all year round. We can help trees if we "take it easy on the salt."