Hydrangeas instantly change colour if gardeners complete these simple tasks

A little known fact about hydrangeas is that you can control whether they turn out pink or blue. All it takes is completing one incredibly simple task.

Hydrangeas are easily one of the UK’s most popular garden flowers. With their graceful halos of bright flowers and sweet fragrance, they add a much needed pop of colour to any home. Even better, you can determine exactly what colour they add. According to garden experts, it’s all down to the soil’s pH.

A soil’s pH basically refers to how acidic or alkaline it is. Depending on the level of acidity of a given soil, different plants will adapt and thrive.

For example, sandy, peaty and woodland soils tend to be more acidic. Meanwhile, chalky, limestone and arid desert soils tend to be more alkaline.

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Hydrangeas sit in the middle, where they can grow in a pH range of between 4.5 to 6.5. The only major impact in varying its pH can be seen in the colour of its petals.

More acidic soils will cause your hydrangeas petals to turn a deep blue. Whereas the higher the alkalinity, the pinker they will appear.

Luckily, this is something that gardeners can determine for themselves. Even better, you don’t have to go and spend money on a new fertiliser.

It's all in the soil

An expert from revealed that you can add certain items to the soil to change its pH. They said: “Technically it isn't a type of fertilizer that changes hydrangea flower colors, it’s soil amendments that change the soil pH.”

They continued: “If you want , apply garden lime, which raises soil pH. For , add aluminum sulfate to the soil, which lowers pH.”

Garden lime is a soil amendment that is typically made from ground up limestone. This will increase the alkalinity of the soil, resulting in a bright pink bloom.

An added benefit is that limestone is also rich in calcium. Calcium is a crucial mineral for most plants, as it helps strengthen cell walls, making them more resilient to stress, pests and diseases.

Conversely, if you’re a fan of blue flowers, you can also make the soil more acidic. A great way to do this is by adding an amendment like aluminium sulfate.

Alum is typically used in water treatment centres as a way to purify water and is safe to ingest. It’s also a known soil acidifier and can be picked up at your local garden centre.

Although, take note that it can be irritating to your skin. So, if you’re using aluminium sulfate in your garden, it’s advisable to wear gloves and a face mask.