How would pH paper help you to predict the color of hydrangea flowers?

The ph will help determine if your Hydrangea will be pink or blue. Now this applies to a lot of hydrangea's there are now variety's where the ph has no or little affect on the color.

That being said if you want a pink hydrangea you need to raise the ph until it is 6.0 to 6.3. You can add dolomitic lime a few times a year until the desired ph is reached or mix baking soda with water and pour it around the plant. Be careful as the ph of baking soda is 7.2 or higher so use a little at first.

Now on to the blue. If you want a blue hydrangea you want to make the soil acidic. You can use aluminum sulphate or magnesium sulphate (epson salt) and either spread the aluminum sulphate according to directions or disolve epson salt in water and pour around plant. You want to careful because you can change the ph to much. Aim for4.5 to 5.0.

Remember it may take a year or two for the change to happen. The reason the color change is aluminum high ph less aluminum low ph more aluminum.

Thanks