Magnesium deficiency on cucumber
A physiological disorder caused by too little magnesium in the soil, or by uptake being disrupted — for example by excess potassium or calcium. It usually shows up in the second half of the season, on heavily cropping plants with a high demand for the nutrient.
Symptoms
- Interveinal chlorosis — leaf tissue yellowing between the veins while the veins stay green
- Symptoms appearing first on the older, lower leaves
- Yellowing turning in time into brown, dead patches between the veins
- Leaves drying and dropping early, starting at the bottom of the plant
- The whole plant looking weak and paler in a severe shortage
What it does to the crop
- Reduced photosynthesis and a generally weakened plant
- Smaller, poorly formed fruit
- Plants ageing early and a shorter cropping period
What encourages it
- Acidic, light, sandy soils low in magnesium
- Overfeeding with potassium or calcium, which blocks magnesium uptake
- Heavy, prolonged cropping raising demand for the nutrient
- Cold soil in early spring limiting nutrient uptake
Prevention
- Feed in a balanced way and include magnesium, for example as Epsom salts
- Foliar feed with magnesium sulphate at the first signs
- Avoid heavy potassium and calcium dressings without topping up magnesium
- Lime acid soils with magnesian (dolomitic) limestone
⚠️ Before you reach for a spray
This atlas is informational and still growing — different diseases can look almost identical. Confirm the diagnosis and read the product label before applying any plant protection product. If you are unsure, ask your local extension or advisory service.
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