How to Change Color of Hydrangea- Pink, Blue, White, Purple

Hydrangea flower clusters can vary in colour in shades of blue, pink, purple, pink and several shades in between. But how to modify the colour of your hydrangea to get blue or pink color?

Follow the simple steps on changing the colour of hydrangea to blue or pink.
Blue Hydrangea Flowers
Blue Hydrangea Flowers

Growing Hydrangeas | Propagation of hydrangea| Caring for hydrangeas| Green Hydrangeas

Changing Hydrangea Colours

The colour of hydrangea depends on two factors:
  1. The amount of light and the shade the plant receives will affect flower colour. Two identical hydrangea plants planted next to each other, one in shade and one in partial shade can have flowers of different tones of colour, even green hydrangeas. However, it is not possible to get red hydrangeas by simply changing the soil pH.
  2. The pH of the soil: The acidity of the soil (i.e. its pH) determines the colour. The chemistry of the soil gives a measure of hydrangea colour change. Following chart is a guide for hydrangeas colour on soil pH:
      pH      Colour
      4.5      Deep blue
      5.0      Medium blue
      5.5      Lavender purple
      6.0      Purple pink
      6.5      Light pink
      6.8      Medium pink
      7.0      Deep pink

So it is possible to change the colour of flowers simply by changing the acidity of the soil. As most garden soils are alkaline so the flowers will be pink. Changing a hydrangea from blue to pink is difficult than changing from pink to blue.

You should have patience because hydrangea colour changes will not occur overnight. Control over the colour of hydrangea in ground is difficult than for potted plants.

To change the pink colour of my hydrangeas to blue, I planted my hydrangeas in pots with azalea potting mix. I also added lot of rotten leaves and aged compost into it. I fed the plant with fertilizers suitable for azaleas.

There are some techniques to reduce the acidity or pH of soil to modify the hydrangeas.

How To Get Blue Hydrangeas

  1. If your soil is highly alkaline, it is impossible to turn a hydrangea blue for ever.
  2. Do not plant your hydrangeas near a wall because the soil pH may be raised by lime leaching out of the wall, making it difficult to obtain blue.
  3. It would be better to grow them in large pots where it is much easier to control the requirements for turning the flowers to blue.
  4. Add lots of compost, rotten leaves, coffee grounds, fruit and vegetable peels and grass clippings to bring the pH down. You may use potting mix and fertilizer for azaleas.
  5. The pH of the water from your tap should not be higher than 5.5. It is a better idea to have your water tested. A dilute vinegar solution may help.
  6. A fertilizer high in potassium and low in phosphorus and nitrogen is helpful in producing a good blue colour. Do not feed your plant bone meal and super-phosphates.
  7. Adding aluminum sulfate will lower the pH of the soil. Apply a solution of 1/2 teaspoon aluminum sulfate in 1 liter of water to the plant throughout the growing season. It is important to water the plant before applying the solution to prevent roots from burning.
  8. Rack some steel wool near the roots to make blue flowers more deep.

How To Get Pink Hydrangea

Pink Hydrangea Flowers
Pink Hydrangea Flowers
  1. For hydrangea blooms to be pink, the plants must not take up aluminum from the soil or you have to raise the soil pH. If the soil of your garden is acidic you should plant hydrangeas in large pots.
  2. For this add dolomite lime (2-3 tablespoon) into the soil around the roots of the plant several times. The exact amount of lime will depend on soil.
  3. To get pink hydrangeas, feed with a fertilizer high in phosphorus.