Potassium deficiency on cucumber
Potassium shortage shows up especially during heavy fruiting, when the plant uses large amounts of it to build fruit. In cucumbers it typically appears as a characteristic fruit deformity.
Symptoms
- Pale discoloration and drying along the edges of older, lower leaves (marginal scorch)
- Leaves doming downwards and turning brittle
- Club-shaped fruit — clearly pinched at the stalk and swollen at the blossom end
- Fruit growth checked and coloring uneven
- Reduced tolerance of disease and water stress
What it does to the crop
- A clear loss of market quality because of the misshapen fruit
- Weakened plants with less resistance to disease
- Lower yield in the second half of the cropping period
What encourages it
- Light soils low in potassium, or with a low pH
- Heavy, prolonged picking that drains soil potassium reserves
- Excess calcium or magnesium interfering with potassium uptake
- Uneven watering that makes the nutrient harder to take up
Prevention
- Match potassium feeding to the heavy fruiting stage, for example with potassium sulphate
- Foliar feed with potassium at the first signs on the fruit
- Keep soil moisture even
- Test the soil before the season and correct shortages in advance
⚠️ 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.
Keep the disease atlas with you in the garden
In the app you can identify a disease from photos, work out the spray dose for your own bed and log the treatment in your task calendar. Free, no sign-up, works offline.
Open the atlas in the app →