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 it 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) or alkalinity (pink) in the soil. Once a plant is purchased the soil pH will be different than your yard. Within a couple of years the Hydrangeas roots will grow into your existing soil and the flower colors will become more consistent. Determining your soil pH will help you to change the flower color. Soil testing kits are available at the nursery otherwise for a more exact test we can provide a soil testing service.

If your hydrangea is installed near pines or oaks the leaves from these trees have a higher acid traces which leach into the soil changing the pH dramatically. Conversely the inflorescence from concrete foundations or walks may sweeten the soil change the pH upwards.  Keep this in mind when locating your newly installed hydrangeas.

Is my soil acidic?

Some Natural ways your soil is acidic:

• Oaks
• Pines
• Acid Rain

To Check your soil pH:

• Use Soil Testing Kits
• Use our Soil Testing Service

How do I turn my soil acidic?

Add Elements that acidify the soil, the more acidic, the bluer the color:

• Apply these products 2-3 times a year
  • Hoffman’s Blue Magic
  • Espoma Soil Acidifier
• General fertilizers
  • Holly Tone
  • Miracid

How do I turn my soil alkaline?

Add Elements that make the soil alkaline, the more alkaline, the pinker the color:

• Apply Lime Stone 6-9 months before it becomes usable by plants
• For quicker results use Liquid Lime

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

My newly purchased hydrangea is not the color I want, why?

Many growers use different container mixes, container mixes vary in Soil pH

• Soil pH is a range from acid, neutral, and alkaline

Test your pH by Soil Tests

• Acid soils are normal in New England
• Alkaline soils are normal in your lawn

Some Varieties of Hydrangea are inherently altered and may not change in flower color including, Pink Elf, Pretty n’ Pink Hydrangea, and more.

Apply products according to the label.
Products provided can be applied at any time depending on soil conditions and the amount of water.
The transformation of color in the flower can be 6-18 months.

By:  Kenneth C. Roth, MCH

Printable Fact Sheet
UMASS has provided Northeast Nursery with downloadable fact sheets for common garden concerns and tips. Hydrangea Color & Fertilizing fact sheet | Hydrangea Pruning fact sheet.

Return to top