Lime-induced chlorosis

What you see

New leaves turn yellow while the veins stay sharply green, giving a fine net pattern. It always starts on the youngest leaves at the shoot tips. In bad cases leaf margins scorch brown and shoots die back.

Conditions

Alkaline or chalky soil, over-liming, hard tap water, or waterlogging - all of which make iron chemically unavailable even where the soil contains plenty of it.

Treatment

A chelated iron (Fe-EDDHA) drench works at high pH where cheaper iron products fail. Seaweed and a mulch of composted bark or pine needles help acidify the root zone over time. Correct any drainage problem first.

Prevention

Match the plant to the soil - acid-lovers in alkaline ground will need feeding forever. Use rainwater rather than hard tap water for pot-grown acid-lovers, and mulch with an acidifying material.

Months: March, April, May, June, July, August

Plants

Orange, Lemon, Tangerine, Blueberry, Camellia, Azalea, Hydrangea, Gardenia, Peach

Remedies

Seaweed extract, Mulch

The thing people get wrong

Green veins on a yellow young leaf is iron; yellow all over on an old leaf is nitrogen; yellow between the veins on an old leaf is magnesium. Getting that one distinction right saves years of wrong feeding. And note the deeper point - iron chlorosis usually means the iron is present but locked up by pH or waterlogging, so pouring on more iron sulphate rarely works while fixing drainage or using a chelate does.