I’ve previously written about how to keep potted Easter Lilies and azaleas alive. Another popular gift plant around Mother’s Day is a potted Hydrangea. Where I live in the South, the most common hydrangeas are peegee and mophead hydrangeas.
Almost any hydrangea that is blue or pink may change its color from one to the other in response to its environment. If a hydrangea is white, it will not change colors. Potted hydrangeas may be kept indoors until the blooms fade, but since the plant is a landscaping plant you should not attempt to keep it indoors for more than one season. Instead the plant should be planted outdoors once the blooms fade.
To keep the plant looking good indoors as long as possible, place it in a sunny windowsill. Check the soil daily and water as needed to keep the soil as damp as a wrung-out sponge. Once the flowers fade, deadhead the shrub and plant the hydrangea outdoors.
Hydrangeas do well in full sun. In their natural environment, they will produce blooms in summer when most other flowers have faded. Sink the plant in the soil so that the top of the root ball is level with the top of the soil and mulch around the roots to help keep them cool and moist during the first season while they develop.
How to Change a Hydrangea Plant’s Color
Hydrangeas change color in response to the amount of aluminum they can absorb in the soil. It is easier to change a hydrangea from pink to blue than to change it from blue to pink. To turn a hydrangea blue, you can add aluminum to the soil. In former times it was popular to bury a nail or tin can around the roots of a hydrangea to do this (You can poke around the roots of an heirloom hydrangea. You may find a number of rusty cans or nails. Just make sure your tetanus shots are up to date before doing this).
To change a hydrangea from blue to pink, you must raise the pH of the soil by adding Lime. This will keep the plant from absorbing the aluminum in the soil and make the plant pinker.
Hydrangeas will also sometimes change colors after being transplanted as they adapt to their new environments.