Nitrogen deficiency

Pale, evenly yellow-green older leaves on a stunted, spindly plant that simply will not fill out.

Disorder Disfiguring Doesn't spread

What you'll see

Uniform pale yellow-green color, whole leaf at once rather than between the veins
The oldest, lowest leaves fade first and may drop early
Weak, spindly, stunted growth with thin stems
Older leaves may take on red or purple tints as they age
Poor yields and small, hard fruit

Why it happens

Nitrogen is very mobile in the plant, so when it runs short the plant moves it out of old leaves into new growth, leaving the lower leaves pale. It is also very mobile in the soil, washing away readily, so it is the nutrient most often genuinely in short supply.

Common on light sandy soils, after a wet winter has leached nitrogen away, on ground with lots of undecomposed woody mulch or sawdust that ties up nitrogen, and on hungry leafy crops grown without feeding.

Treating it

Apply a quick-acting nitrogen feed such as dried poultry manure or a balanced liquid feed
For a fast response on leafy crops, use a soluble high-nitrogen feed watered on
Avoid overdoing it, as too much nitrogen gives soft growth prone to pests and disease
Hold off feeding late in the season so growth hardens before winter

Keeping it away

Build soil fertility with well-rotted manure, garden compost and green manures
Feed hungry crops such as brassicas and sweetcorn through the growing season
Let woody mulches rot down before digging them in, or add extra nitrogen alongside
Improve light soils with organic matter so they hold nutrients better

Who gets it

Leafy and hungry crops feel it most — cabbages and other brassicas, sweetcorn, leafy salads — as do lawns and pot plants left unfed.