Thursday, February 7, 2008

Alternative De-Icing Products Reduce the Risk of Salt Injury on Plants

Rock salt does a good job of deicing sidewalks and driveways, but it can also seriously injure or kill plants growing next to these paved surfaces.

The most obvious damage occurs to turf grass. Rock salt often kills grass leaves, crowns, and roots. Some weeds tolerate the high salt levels, and a common weed called knotweed often moves into areas after the grass dies.

Salt can more subtly damage trees and shrubs growing close to paved surfaces. The soil's high salt content damages the plants' root systems. This causes stunted growth and leaf scorch the following growing season.

Scorched leaves turn brown around the edges and brown tissue develops between the major veins in the leaf. Maple trees commonly display leaf scorch symptoms. The root systems of sugar maples are very sensitive to high salt levels in the soil and often decline over a period of years and then die prematurely.

Salt spray from traffic during winter can accumulate on evergreen needles and twigs and limbs of deciduous trees and shrubs. This often causes evergreen needles to turn brown and fall off.  The plants usually survive, but have only the current season's needles the following summer.  This makes evergreens look rather sparse.

Deciduous trees and shrubs respond to salt poisoning by producing bunchy twig growths called "brooms". Again, this produces deformed growth and possible twig or branch death.

There are many ways to prevent salt injury to plants.  One is to reduce the amount of salt you apply. Most people spread more salt than necessary to do the job. You can also use other materials that do not damage plants.

Materials to try include sand, deicing products with calcium chloride, or even granular plant fertilizer. Fertilizers do a good job of melting ice and may help plants growing near driveways or sidewalks.