Iron chlorosis

also called Lime-induced chlorosis

Yellowing leaves that keep bright green veins, on acid-loving plants growing in soil or water that is too limey.

Disorder Serious Doesn't spread

What you'll see

Yellow leaves with a sharp green network of veins standing out against them
The youngest leaves at the shoot tips are hit first and hardest
In bad cases new growth is almost white, then browns at the edges and dies back
Whole plant looks pale and sickly and fails to thrive despite good feeding

Why it happens

On alkaline soils the iron and manganese acid-loving plants need are present but locked up and cannot be taken in through the roots. It is not a true shortage in the ground but a lack of availability caused by high pH — often from lime in the soil, tap water or nearby concrete and mortar.

Seen on ericaceous plants grown in chalky or limey ground, in pots watered with hard tap water, or where builders’ rubble and mortar have raised the pH. It worsens in cold, wet spring soils when root uptake is already slow.

Treating it

Water with rainwater rather than hard tap water, especially for plants in pots
Apply a chelated (sequestered) iron feed, which stays available even at higher pH
Mulch with acidic material such as composted bark or ericaceous compost
Move badly affected plants into containers of ericaceous compost where you control the pH

Keeping it away

Grow acid-lovers only in ericaceous compost or naturally acid soil, not on chalk
Collect and use rainwater for these plants from the start
Test soil pH before planting and choose lime-tolerant plants for alkaline ground
Keep new plantings away from freshly laid concrete, mortar and rubble

Who gets it

Ericaceous plants suffer most — rhododendrons, azaleas, camellias, pieris and blueberries — along with the occasional wisteria and raspberry on very chalky ground.