How does this differ from Rose of Sharon? I also have it in white and blue. They all have the same leaves and numerous germinating seeds..All bloom at the same time. Maybe what I have is not Rose of Sharon? Does it just have a different common name in UK?
as ecrane said, the common name in the states is Rose of Sharon. if you click on the link above, you'll see many different colors and cultivars.
i always forget that common names here are not the same as common names in other countries.