For established shrubs - Mix the Hydrangea Colourant into the soil at the rate of 50g per square metre. Every 7 days during the growing season dissolve 50g of hydrangea colourant in 5 litres of water and apply to the area of soil covered by the shrub. Do not apply directly on plant foliage. For container-grown Hydrangeas - When potting, mix the Hydrangea Colourant into the compost at the rate of 50g per 5 litres of compost. Every 7 days during the growing season dissolve 50g of hydrangea colourant in 5 litres of water and water the soil round the plant. Best results are obtained with plants growing in acid soils. Where the soil is naturally alkaline use an Ericaceous compost (such as John Innes Ericaceous Compost or Gro-Sure Ericaceous Compost) instead or double the application rate.
