DiseaseOther
Phosphorus deficiency
Slow growth with dull, dark green leaves that develop purple or reddish tints, and poor rooting and flowering.
Also known as: Purple leaves
Symptoms and identification
Older leaves become dark, dull green with purple or bronze undersides and veins. Plants are stunted, roots are weak, and flowering and fruiting are delayed.
Causes
Cold soil, very acidic or alkaline soil that locks up phosphorus, and old, exhausted potting mix.
Organic treatment
Mix bone meal or rock phosphate into the topsoil and water in. Add compost to help release phosphorus.
Prevention
Add bone meal or rock phosphate at planting time, and keep the soil pH between 6 and 7.
Chemical treatment (use with care)
Use a phosphorus-rich fertilizer such as single superphosphate at the label rate.