How to Change My Hydrangea Flower Color

Only Hydrangea macrophylla or serrata species have the ability to change color based on the soil pH. There are some genetically altered cultivars that may stay pink or blue, but this is the exception rather than the rule. There are other species of Hydrangea and the information below will not have any impact on flower color.

Flower color on Hydrangeas is determined by the acidity (blue flowers) or alkalinity (pink flowers) in the soil. When you purchase your plant, the flower color is caused by the acidity of the soil around your root ball, but within a couple of years the Hydrangeas roots will grow into your existing soil and the flower colors may change due to the acidity level in your soil, which might be very different from the nursery yard growing mix in the root ball.

If your hydrangea was planted near pines or oaks, the leaves from these trees have trace compounds which leach into the soil changing the pH dramatically. Conversely the inflorescence from concrete foundations or walks may sweeten the soil, increasing its alkalinity and changing the pH upwards.  Keep this in mind when locating your newly installed hydrangeas.

If you are unhappy with the final color of your hydrangea, you can try to change the acidity around your hydrangea, but first you should have a soil test so you have a baseline. You never want to add amendments unnecessarily.

How do I turn my soil acidic?

Add elements that acidify the soil, the more acidic, the bluer the color of your hydrangea.

• Apply these products 2-3 times a year

  • Hoffman’s Blue Magic

  • Espoma Soil Acidifier

• General fertilizers

  • Holly Tone

  • Miracid

Be sure to follow the package instructions when adding an amendment or fertilizer around your plants.

How do I turn my soil alkaline?

Add elements that make the soil alkaline, the more alkaline, the pinker the color of your hydrangea.

• Apply Lime Stone 6-9 months before it becomes usable by plants

• For quicker results use Liquid Lime

Be sure to follow the package instructions when adding an amendment or fertilizer around your plants.

Why does my Hydrangea turn purple?

Hydrangeas that have red flowers vary in color because of pH, often the flowers look purple or near to purple.

If the flower is purple-red:

• The pH is acidic

If the flower is pink-red:

• The pH is alkaline

To Learn More about Hydrangeas, check out Our Guide to Hydrangea Care!