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How to Make Hydrangeas Blue Using Vinegar

Hydrangeas come in many different colours including blue, purple, pink, red and white. They are the only flowers that can change colour whilst they are still in bloom. In this post I will show you how to make hydrangeas blue using vinegar.

How to Make Hydrangeas Blue Vinegar

How to Make Hydrangeas Blue Using Vinegar

Why do Hydrangeas Change Colour?

The flowers of hydrangeas will change colour depending on the pH level of the soil they are in. If a hydrangea is growing in alkaline soil, it will have pink flowers but if the soil is acidic, the flowers will be blue. The only hydrangeas that won’t change colour are those with white flowers.

The reason why hydrangeas change colour in different pH levels is because the acidity of the soil affects the availability of aluminum to the plant’s roots. Aluminum becomes soluble in an acidic soil, and easier for the plant to absorb. The more aluminum the plant absorbs, the bluer the flower will be.

Why do Hydrangeas Change from Pink to Blue?

The photograph below shows some pink hydrangeas growing in Salisbury, England. The soil in Salisbury is alkaline so the flowers appear bright pink. These flowers would turn from pink to blue if the pH of the soil was reduced, and the roots were able to absorb aluminum.

There are a number of reasons why your soil could become acidic and turn your hydrangeas blue. These could include:

  • Organic matter decomposing in the ground
  • Chemical fertilizers
  • Rainwater drawing calcium and magnesium out of the soil
Pink hydrangeas
Pink Hydrangeas growing in Salisbury – Photograph taken by Barbara Herlihy

What Makes Hydrangeas Turn Blue?

There are only certain types of hydrangea which turn blue. White hydrangeas won’t change colour at all, and some red hydrangeas will turn purple rather than blue.

If you want to grow a blue hydrangea, make sure you have either a Hydrangea serrata (also known as Tea of heaven, or saw-toothed hydrangea) or a French Hydrangea (Hydrangea macrophylla), which can also be known as a bigleaf hydrangeas, lacecap hydrangea, mophead hydrangea, penny mac and hortensia.

The soil pH needs to be between pH 4.3-5, and contain aluminum ions in order to change the hydrangea color from pink to blue.

Two easy ways to achieve blue flowers is to either feed the plants with a fertiliser low in phosphorous and high in potassium, or grow the plants in peat-free ericaceous compost.

In order for hydrangeas to turn blue they need both an acidic environment and aluminum ions. They also need to be in an acidic environment which is sustained over one growing season.

What Home Remedy Will Turn my Hydrangea Blue?

If you want to grow blue hydrangeas but you live in an area where your soil is alkaline, you will need to reduce the pH of your soil, and ensure it contains aluminum ions.

There are home remedies such as coffee grounds, pine needles and apple cider vinegar which can help to make your soil acidic.

What Home Remedy Will Turn my Hydrangea Blue?

How to Use Vinegar to Make Hydrangeas Blue

You can use vinegar to lower the pH of your soil, but be aware that in order to achieve blue blooms, you will need both an acidic environment and aluminum ions.

The acidic environment will also need to be a sustained over a period of time, which could be hard if rainwater is washing the vinegar away.

For this reason I recommend planting your hydrangeas in pots that are under shelter, and using compost with aluminum sulfate mixed in. You will be able to buy aluminium sulfate powder from your local garden center.

Make sure you water the plant with diluted apple cider vinegar or white vinegar, and ensure you only water the base of the plant, as the acid could burn the leaves.

You will need to continue watering the plant with diluted vinegar for several months before you will see results.

Will Vinegar Kill Hydrangeas?

No, vinegar won’t kill hydrangeas. Undiluted vinegar can be used as a natural weed killer to kill certain plants and grasses, but hydrangeas are acid-loving plants that won’t be harmed.

Other plants that like acid soil include rhododendrons, magnolias, and deciduous trees like beech, willow, oak, dogwood, and mountain ash.

Although vinegar can work to lower the soil acidity and make your hydrangea bushes change colour, it probably isn’t the best way. There are other products, like Hydrangea Colourants, which are better at increasing the acidity of the soil and changing pink blooms to blue beauties.

Does Epsom Salt Turn Hydrangeas Blue?

No, epsom salt won’t change the pH of the soil, and won’t have any effect on the color of hydrangea flowers. It may however effect the hydrangea in other ways. For example epsom salt contains magnesium and sulphur which can help the plant grow faster and stronger.

Do Rusty Nails Make Hydrangeas Blue?

Do Rusty Nails Make Hydrangeas Blue?

There is a theory that burying rusty nails in the ground will raise the pH level of the soil, and change the color of your hydrangea from pink to blue.

This idea however is just a myth. If the pH of your soil is naturally high, it will be very difficult to change the acidity to a level that will produce blue flowers – even if there’s plenty of aluminum in the soil.

Using Hydrangea Colourant

Using Hydrangea Colourant to Turn Hydrangeas Blue

The easiest way to change the bloom color of your hydrangea is by using a Hydrangea Colourant. You can buy Hydrangea Colourant from your local garden centre.

This is a powder that you mix into the soil at the rate of 50g per square metre. Every week you add another 50g of the powder to 5 litres of tap water, and pour over the roots of the plant.

The powder will change pink hydrangeas to blue, and dark pink hydrangeas to mauve. It contains nitrogen to produce greener leaves, and potassium to boost flowering.

The Hydrangea Colourant will shift the soil’s pH, but it will take a few weeks for the flower color to change from pink to blue.

Caring for Your Hydrangea

Hydrangeas like to be in soil that contains an abundance of organic material, and has good drainage. They don’t like being in waterlogged or soggy soil, as this can cause root rot.

Hydrangeas also prefer sun in the morning and shade in the afternoon. They also don’t like to be directly underneath trees which can compete for water and nutrients in the soil.

Natural Fertiliser for Your Hydrangea

Natural Fertiliser for Your Hydrangea

Banana peels make great fertilizer for hydrangeas as they contain potassium, calcium, magnesium and phosphorus which help the plant to grow strong roots and stems. These nutrients also help to maintain the overall health of your plants.

To make a banana peel fertiliser, cut three banana peels into small pieces and bury them in the soil around your hydrangea.

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This Post Was About How to Make Hydrangeas Blue Using Vinegar

Thank you for reading my post about how to make hydrangeas blue with vinegar. The color of hydrangeas can be changed with a number of home remedies, but the easiest way is with a Hydrangea Colourant. If you want to change the colour back again, the best home remedy is garden lime which will change the blue color of a hydrangea back to pink.