Aluminium Sulphate – For Blue Hydrangea Blooms

Aluminium Sulphate (Alum) is used to acidify soil and encourage blue flower colouring in hydrangeas. The blue pigment develops when aluminium ions are absorbed by the plant, which only occurs in acidic soil conditions. To achieve vivid blue blooms, ensure the soil pH is 5.5 or lower before flowering begins. A pH between 5.5 and 6.0 is acceptable during early growth, but adjustment is crucial before the forcing stage for the blue effect to take hold.

Benefits:

- Promotes blue flower colouring in hydrangeas
- Acidifies soil to improve aluminium uptake
- Helps manage soil pH in garden beds and potting mixes
- Best used before the flowering period for effective results