The common ingredient can transform the colour of your flowers.Lynn Love Lifestyle Writer and Claire Schofield
10:00, 20 May 2025
This common item will transform the colour of your flowers(Image: Getty Images/iStockphoto)
Hydrangeas are a great option if you want to add a bit of colour to your garden this summer. The bright flowers are very eye-catching and come in a variety of shades and shapes. They tend to bloom from mid-spring until late summer, but this will depend what sunlight you get in your garden and what type of soil you use.
According to the the Royal Horticultural Society (RHS) if the soil in your garden is acidic (with a pH of 5.5 or lower) then then the striking flowerheads will turn blue because of the availability of aluminium, however, alkaline soils (with a pH of 6.5 or higher) tend to turn the flowers pink.
Experts believe you can also change the colour of your hydrangeas if you add coffee grounds to your soil. This will work particularly well if you want vibrant blue flowers.
Because of how acidic coffee grounds are, they naturally lower the pH of the soil. This is what turn the flowers the beautiful shade of blue because the coffee helps to make aluminium more available for hydrangeas to absorb, according to the Express.
Hydrangeas can brighten up any summer garden(Image: Preappy via Getty Images)
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 explains: “Some people report success using coffee grounds to change the colour 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.”
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.
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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.
Gardener’s World adds: “The moist, small particles of coffee grounds are certainly an excellent compost ingredient because of their texture, to mix with dry and woody waste to speed the composting process.
“Ensuring a balanced mix of ‘wet’ and ‘dry’ materials is the best way to achieve good compost. The nutrients contained in coffee grounds will be recycled back into the soil when finished compost is used as a mulch or dug into the soil.
Also, add any un-drunk coffee to dry material in a compost bin.
“Coffee tends to be slightly acidic and is therefore good for acid-loving plants such as hydrangeas, as well as nutrient-hungry plants like roses, but again, use it only in moderation on any one plant.”