Garden Tips: De-icing salt can damage landscape plants

The beautiful pink blooms of my Leonard Messel magnolia will be open almost any day now. I am so glad he made it through the winter unscathed, but I have noted a number of plants in our area that have not escaped the ravages of winter, such as cold temperature injury, sunscald, breakage from snow or ice, and salt burn.

I am betting that we will see salt burn on landscape plants close to roads and walkways where de-icing salts were used this winter. Tons of salt was used to keep roadways and walkways safer, but now we are paying the price for that safety in the form of potholes and damaged plants.

Salt injury on plants occurs in two ways. One is by direct contact with the needles and leaves of evergreens, such as pines and rhododendrons, and with twigs and buds. This type of salt injury is usually the result of salty slush being sprayed on plants by passing vehicles.

Salt in direct contact with buds, twigs, needles, and leaves dries out and kills plant tissues. Salt-damaged buds may be killed or slow to open in spring. Evergreen needles will turn from yellow to brown from the tip back. Parts of the plant that were covered with snow or were higher than the spray’s reach will show less or no damage, and the side of the plant closest to the road will be more severely damaged.

The other way salt injury occurs on plants is through high salt levels in the soil. When soil salt levels are high, water holds onto soil particles more tightly, making it less available to plant roots. This results in drought-like conditions for the plant. High salt levels can also take water out of roots and cause dessication. In addition, high levels of soil salts interfere with the uptake of essential plant nutrients.

Salt ions, such as those of sodium chloride, become separated when dissolved in water. These ions are absorbed by plant roots, and can result in toxic levels accumulating in the plant tissues and causing dessication and death of plant cells.

The symptoms of soil salt injury include dieback of buds and twigs, and marginal leaf scorch, characterized by brown crispy tissues along the edges of leaves and between the veins. Other symptoms of high soil salt levels include stunted growth, poor plant vigor, nutrient deficiencies, chlorotic or yellowish leaves, early fall coloration and dieback.

There is not much you can do about the damage caused by salt spray, except to wait and see what does and does not grow as the season progresses. Prune off dead growth later in the spring. Things may look bleak now, but the plant could rebound.

If the problem is high soil salts, the salts can be leached away with water if drainage is good. In fact, I am willing to bet our rain during the past month has been leaching away much of the salt for us. However, if you think you have an area that is likely to have accumulated high levels of salt, 2 inches of water applied slowly to avoid runoff, and then repeating the same process several days later, should leach remaining salts away.

Winter is finally gone, but not forgotten. In the coming weeks, we will also talk about some of the other types of winter injury that may soon be rearing their ugly heads.

This story was originally published March 26, 2017 at 8:05 AM with the headline "Garden Tips: De-icing salt can damage landscape plants."