Potassium deficiency can affect fruiting plants, and is indicated by a reduction in general growth as well as flowering and fruiting. Leaves may become blue, yellow or purple with brown blotches on the leaf tips or margins. Foliage becomes soft and vulnerable to attack by pathogens. A potash deficiency is more common in light, sandy soils or those with a high chalk or peat content.

Control

Improving soil texture with regular applications of well-rotted mature will help reduce long-term shortages of potassium; short-term deficiencies should be treated with a dressing of sulphate of potash or a high-potash fertilizer.