Garden experts reveal the clever trick that turns hydrangea blooms from pink to blue - and all you need is a tea bag

I love hydrangeas for their beautiful colours, and after finding out how easy it is the change the colour of these gorgeous flowers, I love them even more - as garden experts say all you need is a teabag.

Bright and colourful, it’s easy to see why hydrangeas are one of the most popular shrubs in the UK. If you're agonising over which hydrangea to plant based on the colour, don't bother, as you can change the colour of the blooms by adjusting the acidity of the soil in your garden.

One easy way to do for just 4p is by using a teabag to change the colour of your hydrangeas.

How to change the colour of hydrangeas with a teabag

Hydrangeas are one of the few flowering plants that can change colour.

‘The colour-changing ability of hydrangeas is directly related to the soil's pH level and aluminium availability. When the soil is acidic (pH below 6.0), aluminium becomes more available to the plant, resulting in blue flowers. In alkaline soil (pH above 6.0), the aluminium is less available, leading to pink blooms,’ explains Ted Bromley Hall, managing director of IBRAN Limited.

To know how to change the colour of your hydrangea, you’ll need to know how to test your soil's pH, although it’s a fairly safe bet that if your hydrangeas are pink, you have alkaline soil and vice versa. In acidic soils, hydrangeas can absorb aluminium more easily, which turns the petals blue, while alkaline soils have less aluminium available, which results in pink flowers.

Using teabags will help make your soil more acidic, resulting in blue blooms. It’s an easy method to use, where all you need to do is bury used teabags near the roots of the plants. You could even use the teabags to make black tea to use as fertiliser.

‘Adding tea bags to the soil will change the colour of hydrangeas because the tea contains tannic acid, which lowers the pH level of the soil and increases its acidity,’ says Graham Smith MCIHort, a gardening expert from LBS Horticulture.

Because tannic acid will increase the acidity of the soil, you can only use this method to turn pink hydrangeas blue. If you want to turn blue hydrangeas pink, you’ll need to focus on raising the soil’s pH level and making it alkaline. This can be done by using fire pit ash in your garden, for example.

Is this a good method to use?

The tea bag method is an easy and low-cost way to change your hydrangeas' colour. However, for best results, Graham recommends using aluminium sulphate (£5.35 on Amazon) directly.

‘Although tea bags can be used to change hydrangea colour, a more reliable method is using aluminium sulphate. Whatever you use, the colour transformation will not be instant and will take time, and multiple applications of aluminium sulphate may be required. If your hydrangea currently has pink flowers, the pH change will only affect developing buds so you may not see blue flowers until the following year,’ he says.

For greater control. Ted recommends growing hydrangeas in pots or containers so you have greater control over the soil composition, making it easier to achieve your desired colourway.

What you need

Changing the colour of your hydrangeas is an easy and affordable way to give your garden an update. Will you be testing the method out yourself?