Fertilizer scorch

also called Fertilizer burn, Feed scorch, Salt burn

Scorched, browned leaf margins and dead roots from over-feeding, or from granules and strong feeds landing on wet foliage.

Disorder Serious Doesn't spread

What you'll see

Brown, dried leaf edges and tips, often with a yellow band just inside the scorch
Sharp-edged dead patches where granules or liquid feed touched the leaf
Sudden wilting despite moist soil, as scorched roots fail to take up water
A white, crusty deposit on the surface of compost and around pot rims from salt build-up
Lawns showing dead brown strips or stripes where feed was applied unevenly or overlapped

Why it happens

Fertilizers are salts, and too high a concentration in the soil draws water back out of the roots rather than into them, so the plant dries out from within and the finest roots die. Granules or strong liquid feed sitting on wet leaves scorch the tissue directly. In pots, salts from repeated feeding build up until they reach damaging levels.

Comes from over-generous or too-frequent feeding, feeding dry or already-stressed plants, applying lawn feed in hot dry weather or overlapping passes, and letting feed granules rest on damp foliage. Container plants are especially prone as salts have nowhere to wash away.

Treating it

Flush the soil or compost with plenty of plain water to wash the excess salts through
Brush or rinse spilt granules off leaves and out of crowns straight away
Cut back watering to plain water and hold off all feeding until the plant recovers
Repot badly salt-crusted container plants into fresh compost

Keeping it away

Follow the recommended rate — more feed does not mean better growth, and less is safer
Water plants before and after feeding, and never feed dry or wilting plants
Keep granular feeds off foliage and water them in well
Flush pots through with plain water every few weeks in the growing season to clear salts
Apply lawn feed evenly on a dull, showery day, not in a heatwave

Who gets it

Container plants, seedlings, lawns and salt-sensitive subjects such as houseplants and young vegetables scorch most readily.