Hydrangea varieties such as hydrangea macrophylla and hydrangea serrata can range in colour from pink to blue, with every shade of fuchsia, plum, and periwinkle in between.
However, the blooms can change colour based on the amount of aluminium the plants absorb from the soil, which depends on the soil pH.
High levels of aluminium in the soil plus an acidic soil pH will generate the coveted bright blue to purple flowers.
If there is less aluminium in the soil, it will create a variation of pink blooms.
Not all hydrangea species change colour, however. White ones do not change, and some varieties are bred for a specific colour palette.
The first thing you need to do is test the pH of your soil. Acidic soil (lower pH) will yield blue flowers and alkaline (higher pH) will give you pink flowers.
You can buy a soil test kit on Amazon for £12.99 or from B&Q for £6.99 to determine the pH of the soil.
Once you know the general pH of your soil, you can adjust it to get pink or blue hydrangea blooms.
So what can you use to alter the colour of your hydrangeas? Taking to the Hydrangeas in the UK Facebook page, one gardener shared a photo of her “beautiful” hydrangeas bursting with vibrant blue blooms and claimed it was all down to one kitchen scrap item.
Shanta Patel wrote: “This was a few years ago. Fed with coffee grounds.” she claimed that the plant was originally pink when she bought it from Ikea.
When asked how to apply the coffee grounds to the plant, Shanta said: “Add a layer [of used coffee grounds] on top every month and water it in.”
Shanta was also asked how long it took for her to turn her pink hydrangeas blue, and she claimed she saw results “within the first year”.
To maintain the acidity of your soil, gardeners can also use orange peels, eggshells, or peat if possible.
