What is the problem?

• Many trees--and shrubs--can be disfigured and killed by road salt (sodium chloride), significantly raising tree costs for private and public tree managers.
• The worst damage occurs to sensitive species planted near heavily salted roads with high traffic, especially when they lie downhill, downwind, or have poor drainage.

• Winter: look for "witch’s brooms" (cluster of twigs growing out of branch ends) on deciduous trees, yellow tips on evergreen needles.
• Early Summer: look for marginal leaf scorch on deciduous trees, yellow, brown, or fallen needles on evergreens--especially on the side toward the road.
• Other problems can produce the same symptoms, so examine the whole plant and site.

                                                    Salt damage on sugar maple

• Lower salt levels in the soil slow tree growth and vigor by interfering with nutrient availability and uptake.  Higher levels in trees cause young plant tissues to dry out and die.  In both cases, the chloride ion is the active agent.
• Severe damage on evergreens comes primarily from spray taken up by the needles.
• For deciduous trees, research suggests significant damage also comes from salt being taken up by the roots and by soil structural collapse.

• The following common trees are usually severely damaged by road salt:

• Plant salt-tolerant species such as ashes, callery pears, ginkgo, hawthorns, honeylocust, London plane, tolerant maples (Norway, hedge, or sycamore), English and red oak, tolerant pines (Austrian, pitch, or Japanese black), Sargent cherry, or Scholar Tree.
• Reduce salt application rates, lower the throwing distance, and apply before roads freeze.
• Use a less harmful product such as CMA or Iceban^TM, and mix in inert materials like sand.
• Raise the planting site, or block off the trees from the road with a barrier.
• Improve drainage or adjust grade, so salt is easily leached away from trees.
• Flushing well-drained soils at the end of the winter, or incorporating gypsum or a similar commercial product into the soil before winter begins, has been found to reduce salt damage in some cases.

George Hudler, 1980. "Salt Injury to Roadside Plants," Cornell University Information Bulletin 169.  Most state extensions have available lists of susceptible and tolerant plants.  For other information, advice and help on this topic, call offices of your State Urban Forestry Coordinator or University Extension service, or visit urban forestry web sites.