Road salt injury

About

Rock salt (sodium chloride) used to melt ice burns needles and buds when salty slush splashes or blows onto plants, and it harms roots and soil when salty meltwater soaks in. Plants closest to the road, on the side facing it, are hit hardest.

Also called deicing salt injury, de-icing salt damage, road salt damage, salt injury, salt damage, salt spray injury, winter salt damage

How to recognize it

Symptoms

Salt spray browns or yellows evergreen needles from the tip, kills buds and twigs on the road side, and can cause bushy 'witches' brooms' of new shoots. Salt in the soil works slowly, sometimes over several years: leaves come out small with scorched edges or needle tips, foliage may look blue-green, fall color and leaf drop come early, and plants are stunted. Badly hurt trees can die.

Often confused with

Drought, root damage, winter burn and fertilizer burn look much the same. Damage on the side facing a road, within about 30 to 50 feet of it, or where salty snow was piled, points to salt; soil salt can also cause potassium-shortage-like edge scorch. Ask for a soluble salt test with your soil test to confirm salt in the soil.

Worse when

Fast traffic splashing salty slush, salting late in winter (March), piles of salty snow on beds, poorly drained clay soil, and plants already stressed by drought.

How it spreads

It does not spread from plant to plant. Salt builds up in soil year after year where salty water drains and collects.

When

Spray damage shows in spring; root damage often shows in late summer or hot, dry weather.

Where

Wherever roads, drives and walks are salted in winter; ocean spray causes similar damage along coasts.

What to do, gentlest first

This is not an infection, so sprays for diseases won't help. Fix the cause below.

1. Use less salt, or a gentler deicer Prevent

   Salt only where it's really needed, and mix it with sand so less salt does the job. Calcium chloride or calcium magnesium acetate (CMA) are gentler on plants than rock salt.

   Gentler deicers can still hurt plants. Sweep up heavy sand layers in spring so they don't smother the soil.

2. Keep salty snow and runoff off beds Prevent

   Don't pile shoveled or plowed snow on plants, and steer drainage from drives and walks away from beds.

3. Plant salt-tolerant trees and shrubs near roads Prevent

   Near salted roads, choose tolerant plants such as river birch, ginkgo, black gum, bald cypress, white oak, honeylocust, Colorado spruce, yew and black chokeberry. Keep sensitive ones like eastern white pine, sugar maple, dogwood, burning bush and many viburnums away from spray zones.

   Even tolerant plants can be hurt, and lists differ between sources. Never water with softened water; it is salty.

4. Amend salty soil, by test Prevent

   Gypsum is the usual amendment for sodium salt in soil. Connecticut's Agricultural Experiment Station gives 10 to 50 pounds per 100 square feet, based on the salt test, worked in at least 6 inches deep. Adding organic matter also helps plants tolerate salt.

   Amendments are slow and can't fix very salty soil. Test first.

5. Rinse and flush By hand

   Hose salt off foliage with fresh water soon after exposure. Once the ground thaws, water heavily and repeatedly to push salt below the roots, and prune dead twigs.

   Flushing works on well-drained soil, not on compacted clay.

6. Screen plants from spray Barrier

   Put up burlap, plastic, plywood or window screen on the road side of valued plants for the winter.

Plants it affects

Burning bush, Eastern white pine, Flowering dogwood, Sugar maple, Viburnum