Hydrangea macrophylla and hydrangea serrata are known for their wide range of colours, from pink to blue, including fuchsia, plum and periwinkle. The colour of these flowers can change depending on the amount of aluminium the plants absorb from the soil, which is affected by the soil’s pH level.
When there is a high concentration of aluminium in acidic soil, the flowers will turn bright blue to purple. In contrast, lower levels of aluminium in the soil will produce pink flowers. However, not all hydrangea species experience this colour change. White hydrangeas remain the same colour, and some varieties are specifically bred for a particular colour, according to the Express.
To determine the colour of your hydrangeas, you need to test your soil’s pH level first. Acidic soil (lower pH) will produce blue flowers, while alkaline soil (higher pH) will yield pink blooms. Soil test kits are available for purchase on Amazon for £12.99 or at B&Q for £6.99. Once you know your soil’s pH level, you can adjust it to achieve either pink or blue hydrangea blooms.
But how can you change the colour of your hydrangeas? One gardener shared her secret on the Hydrangeas in the UK Facebook page. Shanta Patel posted a photo of her vibrant blue hydrangeas, attributing their colour to coffee grounds. She revealed that the plant was initially pink when she bought it from Ikea.
When asked about using coffee grounds for plants, Shanta explained: “Add a layer [of used coffee grounds] on top every month and water it in.” She also noted that she saw changes in the colour of her hydrangeas “within the first year”.
To maintain the soil’s acidity, gardeners can also consider using orange peels, eggshells or peat. For faster results, aluminium sulphate is a reliable option to turn pink hydrangeas blue. The Trustleaf 1kg Tub Aluminium Sulphate, available on Amazon for £9.90, has been praised by customers who successfully turned their hydrangeas blue and kept the colour.
Another option for garden enthusiasts is the Hydrangea Colourant from Thompson & Morgan, priced at £5.99, which is also effective in changing pink hydrangeas to blue.
