I've heard that if you put...

Question

I’ve heard that if you put the tea from old tea bags on hydrangea plants, the blossoms will turn blue or purple. I have four of these plants with pink blossoms, and I was wondering whether the tea would change their color.

Answer

Hydrangea flowers are pink in near-neutral soil and blue in acidic soil. You can change the color of the flowers by changing the pH of the soil. If you have a lot of lime in your soil, the blossoms will be pink. To get blue flowers, you need to lower the pH, which you can do by adding sulfur or peat moss to the soil. Adding tea, which contains tannic acid, also might bring on the blue color.