Change the Color of Hydrangeas

Hydrangeas are a beautiful addition to a garden. And you can manipulate the color that they display by simple additions of different nutrients.

Steps

Add a sprinkling of lime around the hydrangea for pink flowers. 2 or 3 limes will work.
Add a tablet of aluminum sulfate to the watering can used for watering the hydrangea. This will result in blue flowers. The water pH should be no more than 5.6 or it will affect the results.
Bury steel wool under hydrangea bushes. This will make blue flowers more vivid. Make sure you don't interrupt any insects or animals (For that matter, Anything) Critters could chew it. Put it near the roots.

Lime or the aluminum sulfate tablet should be available at your local garden center.
Control over the color is easier for potted hydrangeas than for ground-planted plants. In particular, forcing pink hydrangeas is easier in potted form.
Don't try manipulating white hydrangeas; you can't change them. Some pink will show through naturally of its own volition but you won't be able to force any color change.
Changing a hydrangea from pink to blue is easier than changing it from blue to pink.^[1]