The SCIENCE of Hydrangea colors
You may think that once you plant a seed, the color of the flower you chose, is the color that you will always have... THINK AGAIN! A miraculous scientific breakthrough (not really... but science nonetheless), we have harnessed the power to change the particular hue of a hydrangea very simply. First the facts - There are many types of Hydrangeas that come in many colors, but here in New England, we are accustomed to seeing the large leaf balls (as seen below) and they tend to be pink, blue, or a mix of both. You will also see whites and yellows as well as a few different shapes.
"Hydrangea Blue" as it has come to be known, is such a unique color, it has not been discovered on any other naturally occurring species on earth. For this reason many people want to have blue hydrangeas but the plants don't always seem to cooperate - but there is a reason, and a solution!
The color of a particular hydrangea is determined by the soil content in which the plant is growing. More specifically, it has to do with the acidity (pH) level in the soil. The lower the pH level, the higher the acidity - not particularly important for this conversation, but a tidbit you've likely learned and forgotten, and will forget again...
Here's the important part: Blue hydrangeas grow in acidic soil, pink grow in alkaline (opposite of acidic) soil.
How to alter the acidity of your plant's soil - If you have pink hydrangeas and would like to turn them blue, here are a few things you can mix into the soil that you likely would've throw away anyway:
- Used coffee grounds
- Ground citrus peels
- Egg shells
- Leaf compost
- Vegetable compost
- If the slower compost strategy is not what you were thinking, adding diluted aluminum sulfate to the soil will accomplish the same goal, likely much quicker.
If you desire the opposite effect, your typical garden shop lime will reduce the acidity and add more pink to the hydrangeas.