Hydrangeas: Blue, Pink, or Purple

Some of my GARDENS4U  gardens have blue hydrangeas and some have pink hydrangeas.  A garden I was at recently had both.

We all know that blue and pink together make purple, so I was not surprised to see a few pale purple blossoms within the garden…

What Does the Blossom Colour Depend on?

The colour of your hydrangea blooms depends on the pH of your garden soil.

If you prefer your hydrangeas to be pink, make your soil alkaline (pH of 6.0-6.2)  You can do this by adding garden lime to your soil.

If you would rather your hydrangeas be a blue color, lower your soil’s pH to the acidic side (between 5.2 and 5.5).  Acidic soil can be achieved by adding 1/2 cup of wettable sulfur powder or other commercial soil acidifiers each spring.  Pine needles or pine bark applied as a mulch also creates acidic soil conducive to blue hydrangeas.  So does compost or composted manure.  Some gardeners have had success using coffee grounds to provide acidic soil around their hydrangeas.

Testing Your Soil to Determine its pH

So, how do you know if your soil is acidic or alkaline?  Try this simple soil pH test using ingredients from your kitchen:

• Collect soil from different parts of your garden.  If you have a large garden, you may want to label your containers.  Styrofoam cups work well.
• put 2 spoonfuls of soil into each of the several containers.  (Two containers for each location)
• Add 1/2 cup of vinegar to the soil in one container.  If it fizzes, you have alkaline soil, with a pH between 7 and 8.
• If it doesn’t fizz after doing the vinegar test, then add distilled water to the other container taken from the same location until the 2 teaspoons of soil are muddy. Add 1/2 cup baking soda. If it fizzes you have acidic soil, with a pH between 5 and 6.
• If your soil doesn’t react at all it is neutral with a pH of close to 7.

Experiment with Soil pH

Once you get your soil’s pH figured out, try adding the appropriate soil amendments to just one side of a hydrangea bush to see if you can get both pink and blue blooms on one plant; perhaps you will end up with purple!