Iron deficiency (lime-induced chlorosis)
Iron is plentiful in most soils but becomes unavailable as pH rises. Acid-loving plants in chalky soil, or watered with hard tap water, cannot take it up, and their new leaves go pale yellow with a green net of veins.
Soil & nutrients
What it looks like
The newest growth shows it; old leaves stay greener.
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Green-veined young leaves A fine green network on yellow leaf tissue at the shoot tips. -
Pale shoot tips Severe cases turn new leaves cream or white. -
Browned edges Leaf margins scorch in long-standing cases. -
Weak growth Shoots are short and crops poor.
How to confirm it
The pH test usually settles it.
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New leaves first
Interveinal yellowing starting at the top of the plant points to iron (or manganese).
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Test the pH
Blueberries want pH 4.5 to 5.5. Anything near 7 or above explains the yellowing.
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Check the water
Pot plants watered with hard tap water drift alkaline over a season.
What to do
Correct the soil, and feed iron in a form the plant can use.
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Sequestered iron
Apply a chelated or sequestered iron product as a drench; new leaves green up within weeks.
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Water with rainwater
Collect rainwater for acid-loving plants in pots.
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Acidify gradually
Work sulphur chips into the soil, or repot into ericaceous compost.
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Grow in containers
On chalk, grow blueberries in pots of ericaceous compost rather than fighting the soil.
Prevent it next time
- Test soil before planting acid-lovers.
- Use ericaceous compost and rainwater for blueberries.
- Avoid mushroom compost and lime near acid-loving plants.
What not to do
Do not use ordinary iron sulphate on alkaline soil and expect lasting results; only sequestered iron stays available at high pH.
In the growing guides
Where the guides mention it, with plant-specific advice.
Sources
- Chlorosis, Royal Horticultural Society
- Nutrient deficiencies, Royal Horticultural Society