Nitrogen deficiency
Nitrogen builds leaves. When it runs short the plant moves what it has from old leaves to new, so lower leaves turn pale yellow, sometimes flushed red, while growth slows. Leafy crops and corn show it first.
Soil & nutrients
What it looks like
The yellowing is even across the leaf and climbs the plant from the bottom.
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Pale older leaves The lowest leaves turn light green then yellow, veins and all. -
Reddish tints Brassica and corn leaves can flush red or purple as nitrogen falls. -
Small new leaves New growth is thin and undersized. -
Stalled growth Plants look stuck at one size for weeks.
How to confirm it
Its pattern is distinctive.
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Old leaves first
The yellowing starts at the bottom and is uniform, not between veins.
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Whole plant pale
The entire plant is lighter green than it should be.
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Quick response
A liquid feed greens new growth within 7 to 14 days.
What to do
Feed, and keep the soil fed.
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Liquid feed
Use a high-nitrogen liquid feed or seaweed and fish mix, every one to two weeks for leafy crops.
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Top-dress
Scatter a nitrogen-rich organic fertiliser such as chicken manure pellets and water it in.
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Mulch with compost
Well-rotted compost or manure releases nitrogen slowly through the season.
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Remove the worst leaves
Fully yellow lower leaves will not green up; take them off once new growth is healthy.
Prevent it next time
- Dig in compost or manure before sowing hungry crops.
- Follow peas and beans with leafy crops.
- Do not dig fresh wood chip into the soil; use it on paths or as a surface mulch.
- Feed container plants regularly once their compost is spent.
What not to do
Do not overcorrect on fruiting crops. Too much nitrogen gives leaves instead of flowers.
In the growing guides
Where the guides mention it, with plant-specific advice.
Sources
- Nutrient deficiencies, Royal Horticultural Society