By altering the soil pH with vinegar, you can actually turn your pink-flowering hydrangeas blue! For this trick, simply dilute your vinegar in water before pouring it around the base of your hydrangeas, and within just a few weeks you could have fresh and bountiful blue blooms.

How to Turn Pink Hydrangeas Blue. To make the change from pink to blue, grow the plant in a container and lower the soil pH level to 5.6 by adding aluminum sulfate. Choose the Right Type of Hydrangea. Start with Bigleaf (H. macrophylla) or Mountain (H. serrata) hydrangeas with medium or light pink, purple, or blue flowers. Grow in a Container

If your hydrangeas are pink (because your soil is alkaline) and you want them to be blue, you need to make the soil acidic by increasing the presence of aluminum. You can achieve this by adding amendments to you your soil like pine needles, compost, coffee grounds, and aluminum sulfate that help make the soil acidic over time.

The more alkaline the soil, the pinker the flowers. To make pink hydrangeas turn blue (or to keep your blue ones from turning pink), increase the acidity of soil. To confirm your soil’s pH level, let’s test a sample: