What Makes Hydrangeas Pink

If you have ever tried to plant a garden, you most likely have looked at a plant nursery catalogue and wondered what colour flowers you'd like to see every day as you are enjoying your morning coffee. You carefully curated your saplings and seeds, cared for the plants, and waited impatiently for them to bloom. All that effort to see beautiful pink hydrangeas bordering your house, just for them to turn out blue. Why does this happen?

These aren't even flowers

Did you know that what we consider the hydrangea flower isn't a flower at all? In fact, it's a different kind of foliage that are modified sepals, the leaves that encapsulate the flower to protect the bud right until it's time for it to bloom. The actual flowers on your typical hydrangea are small and barely noticeable. Of course, since the sepals take up all of our attention, and as a result, by the time the flowers bloom, we have already enjoyed the gorgeous globe-shaped inflorescence.

What determines the colour of hydrangeas?

The hue of your hydrangeas depends largely on the right combination of soil pH and a few other components. It's all about the biochemistry that unfolds within the plant. It's like a nature's chemistry lab, but instead of a litmus paper, we have the hydrangea's sepals.

So what colours should you expect on your hydrangea? Acidic soil with a pH of 4.5 produces bright blue hydrangeas. As the acidity of the soil decreases and pH rises to 5.5-6, expect to see the flowers turning pink. At 7 pH, you'll get a vibrant pink colour.

Equipped with this knowledge, you can control what colour hydrangeas grow in your garden. To increase acidity, add sulphur, gypsum, or aluminium sulphate. To lower acidity, add garden lime. If you prefer to only use natural ingredients in your garden, to increase the acidic quality of your soil, use vinegar, coffee grounds, or lemon juice. You can even try and get different coloured flowers all on the same plant.

Start experimenting in autumn, and you might even see the results of your efforts by the following blooming season. Keep persisting for the desired colours to take full reign over your flower garden.