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Fertiliser burn: how to recognise and treat it

Growing conditions

Fertiliser burn — Photo: Cityside189, CC BY-SA 4.0, Wikimedia Commons

Symptoms

The tips and edges of both young and old leaves turn brown and dry; the damage is spread evenly over the plant.
Wilting and slowed growth, because salts around the roots make it harder for the plant to take up water.
Tender shoot tips may be killed.
In pots, a whitish or brownish crust builds up on the compost surface or the inside rim of the pot.

Organic treatment

Water a pot plant heavily and let the water drain away from the pot to wash out some of the salts; this works only for quick-release and liquid fertilisers.
Scrape off the salt crust and add fresh compost, or repot the plant in fresh compost.
Stop feeding until the plant recovers, and empty the saucer after watering.
Use rainwater for pot plants where you can.

Chemical treatment

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Feed moderately, according to the plant's needs and the label; a soil test shows what nutrients are already there.
Apply fertiliser to moist soil and water it in thoroughly.
Never feed plants stressed by heat or drought, and do not let dry or granular fertiliser touch wet leaves.
Leach pot plants with plenty of water from time to time and repot them in fresh compost periodically.

Sources

Figures checked against these sources.