Top News

Hydrangeas are a favourite for British gardens. Their huge luxurious blooms provide a stunning burst of colour, and they are relatively easy to care for.

They are also one of the few garden plants that can change colour over time. Many people buy these plants and assume that their colour is fixed, but certain varieties can shift over time. With the right soil, hydrangeas can change from pink to blue or even purple. This happens when the soil is more acidic which makes aluminum more available to the plant, which can affect the petals pigment.

Jo McGarry, from Caragh Nurseries, said: "Many people are surprised to learn that hydrangea colour is directly linked to soil pH. In acidic soil, the blooms turn blue, while alkaline soil encourages pink petals. Purple shades appear when the soil is close to neutral.

"Only certain hydrangeas respond this way, particularly macrophylla and serrata varieties. White hydrangeas generally stay white regardless of soil conditions."

If you want to change the colour of your hydrangeas, it's simple enough to do. However, certain old-fashioned methods should be avoided.

One way gardeners have tried to change the colour of their hydrangeas is by burying a rusty nail into the soil beneath their shrubs.

Jo said: "Burying rusty nails in the soil to turn hydrangeas blue is something gardeners have talked about for years, but it isn't the safest or most effective option.

"Sharp metal hidden in borders can become a hazard for people and wildlife. They also provide too little soluble iron to impact petal colour."

Instead, there are safer ways to switch up your garden.

Jo said: "Using ericaceous compost, coffee grounds, or aluminium sulphate is a much better approach for gardeners wanting blue hydrangeas. These methods gently increase soil acidity without creating unnecessary risks in the garden.

"For pink hydrangeas, the soil needs to be more alkaline. Adding garden lime can help raise the pH and reduce aluminium uptake. This encourages pink blooms to develop.

"A fertiliser with higher phosphorus levels can also help limit aluminium absorption and support stronger pink colouring."

It usually takes at least one growing season for noticeable colour changes to appear.

Jo said: "Testing your soil pH first is always worthwhile because overcorrecting can stress the plant and affect nutrient uptake. Small gradual changes tend to give the healthiest and most consistent results."