Hydrangeas are some of the most beloved flowering shrubs around the world and you only need one look at their big, voluminous flower heads to see why they’re so easy to love.
These plants have the incredible ability to change colour, however, this does not apply to all varieties.
Some kinds of hydrangea only come in white, but other varieties like mophead hydrangeas can be blue, pink, red, or purple.
According to the experts at Eising Garden Centre, the flowers of the mophead hydrangea change as a reaction to their soil chemistry, resulting in flowers from bright pink to neon blue and every shade in between.
However, the shift in shade doesn’t happen overnight. It requires some planning, and a fair bit of patience, to change your hydrangea’s colour.
Changing your soil pH requires the use of soil amendments, which can gradually alter the soil chemistry.
The experts explained: “If your hydrangeas are blooming pale pink to lilac, you can intensify the pink colour by adding garden lime to the soil.
“Follow the package directions to ensure you’re using the right amount at once, and over time, those hydrangeas will start blushing.”
However, most mophead growers are in it for the blue blooms. Blue is a relatively uncommon colour in the gardening world, so those gorgeous blue blooms are highly coveted.
Mopheads start “blooming gorgeous blue flowers once the soil pH reaches 5.5 or lower”.
The gardening pros explained: “The best way to increase the acidity of the soil is with the use of aluminium sulfate, a common soil amendment.
“You’ll need to mix a quarter-ounce of aluminium sulfate into a gallon of water and soak the soil around your mopheads.”
“You’ll get the best results by starting in spring, but you can start at any point during the season.”
Gardeners can pick up the Trustleaf 1kg Tub Aluminium Sulphate from Amazon for £9.90. This product has received many great reviews from customers who have turned their hydrangeas blue and kept them that colour.
Alternatively, gardeners can purchase the Hydrangea Colourant from Thompson & Morgan for £5.99 which also changes pink hydrangeas to blue.
However, once gardeners start treating the soil, they’ll need to reapply the amendment every month until they reach the desired result, and then maintain it with an application every other month during the growing season.
To maintain the acidity of your soil, the gardening expert pointed out that fertilising with acidic compost like orange peels, coffee grounds, eggshells, or peat is possible.
While “you won’t see results right away”, these will help increase soil acidity in the long term, so that “you eventually won’t have any need for the aluminum sulfate”.
