Only hydrangea macrophylla (bigleaf or mophead hydrangeas) flowers can turn purple. This is caused by the pH of the soil In slightly acidic or neutral conditions (pH 6 to 7). Some hydrangeas will keep purple even in different soil conditions, but that happens less frequently.
Purple Hydrangea Meaning
Purple hydrangeas symbolize a desire to understand someone deeply. It can also be a symbol for someone with an abundance of wealth.