Salt damage

also called De-icing salt injury, Soil salinity

Brown, dead leaf edges and dieback on the side of a plant facing a road or a drive. Salt from winter grit, or built up in a pot from years of hard water.

Disorder Serious Doesn't spread

What you'll see

Leaf margins and tips browning and drying while the middle of the leaf stays green.
Damage sharply worse on the side of the plant facing a road, drive or path.
Evergreens browning from the outside of the needle inward, worst up to the height the spray reaches.
Buds killed and shoots dying back, then a witch-broom of small crowded shoots the following year.
On container plants, a white crust on the pot rim and the soil surface, and leaf edges burnt on every side.

Why it happens

Two different injuries with the same cause. Salt spray thrown up by traffic burns the tissue it lands on directly. Salt washed into the soil raises its osmotic strength so the roots cannot take water up even from wet ground, and sodium displaces calcium and magnesium from the soil, wrecking the structure into the bargain. In pots, the salt is fertilizer residue and hard water rather than road grit.

Within about ten meters of a salted road or path, and further where traffic is fast. Coastal gardens get the same from sea spray. In containers it builds over a season or two of feeding and watering with no leaching.

Treating it

Leach the soil heavily in early spring: a good soaking of clean water, repeated, washes sodium down and out of the root zone.
Flush containers by watering until it runs freely out of the bottom, three or four times over, and scrape off the crusted surface.
Apply gypsum to a salt-damaged soil, which replaces the sodium with calcium and restores the structure.
Prune out dead shoots after the spring flush shows what has survived.
Water and mulch through the following summer; the plant is short of water even when the soil is wet.

Keeping it away

Use sand, grit or calcium magnesium acetate on paths near planting rather than rock salt.
Put up a burlap or plastic screen along the road edge for the winter.
Plant salt-tolerant species in the front line: rugosa rose, sea buckthorn, juniper, honey locust, ornamental grasses, daylilies.
Keep the most sensitive plants — pines, spruces, maples, roses — well back from a salted road.
Leach containers every couple of months through the growing season and repot in fresh compost each year or two.

Who gets it

Anything within salt-spray range of a road; conifers, maples and roses are especially sensitive, and any container plant fed for a season without leaching.