In order for the flowers to turn pink, they need alkaline soil, that is, with a pH of more than 6.5. For this, put 2 teaspoons of baking soda in your watering can. Water the hydrangea with this mixture about once a month. Over time, the soil will become more alkaline. The flower will then take on pink and red reflections.

For the flowers to turn blue, more acidic soil with a pH between 4.5 and 5 is needed. To do this, dilute 2 cups of white vinegar (about 500 ml) in 4 liters of water. Then, water the hydrangeas with this mixture. Adapt the quantities of vinegar according to the size and age of the plant. If it is in a jar, put less vinegar. Then place the plundered slate at the foot of the hydrangea and let it act. You can also replace the slate with rusty nails. Plant them in the ground towards the roots. There is also a powder of aluminum sulfate on the market, to be diluted in water to obtain the same effect. The only difference is the higher price.

Which hydrangeas to choose?

Panicle hydrangeas ( Hydrangea paniculata ) stay white and turn pink as they age. Rough hydrangeas (Hydrangea Aspera), with hairy foliage, also do not change color by correcting soil pH.
Only Hydrangea macrophylla hydrangeas and Japanese hydrangeas ( Hydrangea Serrata) can vary depending on the soil. You can then change the colors from one year to the next.