Blue hydrangea blooms are the envy of many gardeners, but the path to achieving blue sepals may be easier than you think.
It is believed many hydrangea crops can take on a blue hue when grown in the right conditions, and experts argue it all boils down to the acidity of the soil.
In essence, hydrangea flowers – which exist in a rainbow of shades – produce bluer blooms when grown in acidic gardening soil and pinker ones in alkaline soil.
Experts at All About Gardening have previously discussed different ways to alter the acidity of the soil using common household ingredients like eggshells, coffee grounds, and vinegar.
The green-thumbed enthusiasts say the flowers are more likely to take bluer hues if their soil is frequently treated with vinegar to lower the pH levels.
The website Garden Design adds “many gardeners add vinegar to their watering” to “change the acidity of their soil and turn their hydrangeas blue.
However, the gardening body adds that “you’ll probably have better results using Hydrangea Blue, a liquid fertilizer that produces blue flowers”.
Diluted vinegar will only lower the pH levels enough to change the colour of hydrangea flowers if the soil is treated consistently and frequently, however.
Although the ingredient is commonly used as a weed killer, hydrangea flowers are acidic by nature so don’t risk getting harmed by the ingredient.
It should also be noted that while the roots will come to no harm when vinegar is applied directly to the soil, contact with hydrangea leaves should be minimised at all costs.
This is because the acetic acid in vinegar can burn through the wax coating of sepals if sprayed directly onto them.
The website Hydrangea.com points out in the event of rain, however, vinegar can quickly dilute, making little to no difference to the pH levels of the soil.
“For your hydrangeas to change color [sic] they need a pH change sustained over a long time,” explains the website. “It could take even longer than one growing season! Every time you water, you would have to add vinegar to your soil to maintain the pH.”
Furthermore, the most common ingredient used by gardeners to raise the pH level of soil is ground lime, and sulfur or ammonium sulfate to lower pH levels.
