ROAD SALT AND TREES

    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 or have poor drainage.

     

    How can salt damage be recognized?

    • Winter: look for "witch's brooms" (cluster of twigs growing out of branch ends) on deciduous trees, yellow tips to 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.

     

    How does the damage occur?

    • Low levels of salt slow tree growth and vigor by interfering with nutrient availability and uptake in the soil. Higher levels cause young plant tissues to dry out and die.
    • Severe damage on evergreens comes primarily from spray taken up by the needles.
    • For deciduous trees, it is caused primarily by salt being taken up by the roots.

     

    Which common urban species are sensitive?

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

    red maple (Acer rubrum)

    Norway spruce (Picea abies)

    black walnut (Juglans nigra)

    white pine (Pinus strobus)

    sugar maple (A. saccharum)

    Douglas fir (Pseudotsuga menziesii)

    hackberry (Celtis occidentalis)

    white spruce (Picea glauca)

    littleleaf linden (Tilia cordata)

    pin oak (Quercus palustris)

     

     

    What can I do about it?

    • 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, 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.

    • Sometimes flushing well-drained soils at the end of the winter, or incorporating gypsum or a similar commercial product into the soil before winter begins, reduces salt damage.

     

    Where can I get more information?

    George Hudler, 1980. "Salt Injury to Roadside Plants," Cornell University Information Bulletin 169.

    If you want this publication or other information on this topic, call your regional DEC, Cooperative Extension, or DOT--or us at the Community Forestry Education Project, 716-461-1000.