Gardeners looking to transform their hydrangeas into a vivid blue display don’t need any expensive soil treatments, an item sitting in your pantry will do the trick. According to gardening blogger Mel, who writes Little Terraced House, apple cider vinegar can be a simple, inexpensive way to turn pink blooms into striking blue ones.
Mel said that the iconic hydrangea flower, which is often seen in shades of pink, blue, or even mauve, is actually the same plant. Its colour depends largely on the pH level of the soil. Alkaline soils produce pink flowers, acidic soils produce blue blooms, and neutral soils result in mauve or purple.
“You can test your soil with a cheap pH testing kit from any garden centre,” Mel said.
“It will also be fairly obvious from the colour of your hydrangea!” For gardeners seeking the elusive blue shade, acidifying the soil is the goal.
The method is fairly simple, mix one cup of apple cider vinegar with 10 litres of water (roughly one full watering can) and pour the solution directly at the base of the hydrangea every couple of weeks, being careful to avoid the leaves.
The colour change won’t be instant, but over time the blooms will gradually take on a richer blue. Once the desired shade is reached, the vinegar can be reduced or stopped altogether.
“You can control the ‘bluing’ by adjusting how much you use,” Mel added.
The trick works for plants grown in the ground or in pots. For container-grown hydrangeas, using ericaceous compost from the start will give them a head start towards blue. Mel added that she enjoys combining different varieties together, such as a white hydrangea in a pot alongside a large pink-and-blue specimen growing in the soil.
She did caution that too much vinegar could damage a plant’s roots, so moderation is key. But in her experience, the technique has never caused harm.
“It’s a surprisingly simple trick,” she said. “You don’t need pricey products or long waits, just a splash of vinegar and a little patience.”