Beware of salt injury to plants this winter

By Eric Barrett

OSU Ext. educator

Remember the salt you are using to melt slippery sidewalks and the crews are using on our dangerous roads? It is a necessity in winter. Without it, travel would be difficult. But it can cause serious plant damage when washed off into surrounding soil.

Basically, salts can accumulate on leaves, stems and buds or build to toxic levels around the roots. Over time, salt burn weakens the entire plant and causes droughtlike symptoms.

Injury attributed to road salt spray is particularly evident on conifers along roadways. Salt used to treat icy roads becomes airborne and affects plants 100 to 150 feet from highways, depending on the force and direction of the winter wind. Salt damage on evergreens tends to appear in late winter and worsens in early spring. You may have noticed this in your own yards if you are near a major road.

Evergreen needles turn progressively brown from the tips toward their base. Damage to deciduous plants was not apparent until bud break, when bud and branch dieback was noticed. Classic symptoms of airborne salt injury appear on the side of the plant facing the salted highway.

Injury from airborne salt spray is caused primarily by cell and tissue sensitivity to the chloride ion. Chloride moves in the transpiration stream to leaf tips and margins and may accumulate there in toxic concentrations. Salt injury from salt runoff into soil is more complex. Toxic accumulation of ions in plant tissues may occur, but salts also increase the osmotic potential of the soil solution, which can severely impair the ability of roots to absorb water and nutrients. Roots, in essence, experience drought in high salt soils, even when moisture is available.

What can you do to help reduce this injury to plants in your landscape?

You might consider using barriers to protect plants near heavily traveled roadways, driveways or sidewalks – or be cautious about how close plants are to these areas. Also, pick plant material that is not sensitive to salt injury. Our OSU Extension horticulturalists say sensitive plants include azalea, rhododendron, beech, river birch, boxwood, black cherry, cornelian cherry, cotoneaster, crabapple, dogwood, Douglas fir, white fir, sweet gum, forsythia, hemlock, hickory, American holly, common lilac, red and sugar maple, eastern white pine, flowering plums, flowering quince, Allegheny serviceberry, white spruce, sycamore, tulip tree and yew.

On your sidewalks and driveways, you might consider using alternative ice-melting materials such as coarse sand, sawdust or wood ash. Just remember to wipe your shoes before walking into the house!

For details on salt damage and a list of salt-tolerant plants, visit http://go.osu.edu/salttolerant.