If you’re keen to add a burst of colour to your garden then hydrangeas are a great option to choose as they’re both eye-catching and come in a variety of shades.
The flowers typically bloom in mid to late summer, with blues, pinks, purples and whites being the most common colours, but the colour can actually be dependent on the type of hydrangea you choose and the type of soil you plant it in. Hydrangeas are unique not only for their striking cone and ball-shaped flowerheads but also because certain varieties can change colour. Bigleaf hydrangeas (Hydrangea macrophylla) and mountain hydrangeas (Hydrangea serrata) have the ability to change their flower colour depending on the pH level of the soil.
This is great news for gardeners who want to add a pop of blueinto their garden as this colour flower is considered pretty hard to come by. True blue flowers are rare in nature with fewer than 10% of flowering plants having this colour, making hydrangeas that extra bit special.
Hydrangeas can change the colour of their flowers due to the pH levels of the soil, with acidic soil producing blue and purple flowers and alkaline soil resulting in pink or red blooms. White hydrangea varieties generally stay white regardless of the soil pH levels.
So if you’re eager to get striking blue blooms in your garden throughout the summer, you can alter the pH of your soil to make it more acidic to produce this colour. According to gardening experts, sprinkiling coffee grounds in your soil is one way to achieve this.
Coffee grounds are acidic and so they naturally lower the pH of the soil to make it more acidic, which is key to producing blue flowers. The common kitchen ingredient also helps to make aluminium more available for hydrangeas to absorb which in turn helps promote striking blue blooms.
Gardenia explains: “Coffee grounds can help make soil more acidic, which can contribute to turning hydrangeas blue. When added to the soil, coffee grounds release nitrogen and may slightly lower the pH, promoting blue colouration in varieties like Hydrangea macrophylla.”
Experts advise sprinkling coffee grounds around the base of hydrangeas, but make sure they aren’t directly in contact with the stems of the plant. Then gently work the coffee grounds into the soil using your hands or a trowel to help them break down.
Coffee grounds can also be composted before being applied to the base of the plant as this can help provide a wider range of nutrients and improve the health of your soil.
Gardeners should note that the process won’t happen overnight and will require some time and patience to produce the blue colour, so if you want to give the plant an extra helping hand adding aluminium sulfate to your soil as well can really help.
Planting Tree adds: “Some people report success using coffee grounds to change the color of their hydrangeas. Coffee grounds, in theory, carry enough acid to increase the acid in your soil to change your hydrangeas to blue hydrangeas.
“This method may work, and coffee grounds break down into the soil well, so there’s no harm in trying it. However, if you want to give yourself better odds of results, you might consider a product specifically designed to increase the acidic balance of your soil.”