i have seen a few tree versions at our big box home improvement stores. I am not sure if that would be similar in the UK. Hibiscus is not naturally a tree that i am aware of, so the ones that you see have been either grafted or grown specially to make them into trees. I don't see them that often and usually only in our spring/summer season.

I wonder if you are thinking of Althea or Rose of Sharon? they are showy trees that are winter hardy and lovely accent trees. Of course not such large blooms as hibiscus.

Hi, I am writing in from Vienna, Austria. we planted two lines of young hibiscus in April in our garden and they are growing fine. However, winter is approaching and we are scarred of losing them to the usually harsh cold in Austria. WHAT SHALL WE DO TO PROTECT THEM THIS WINTER????????

Hi danjuma, do you know if you have the ornamental tropical hibiscus shrub or the rose of Sharon tree? If you have the ornamental variety I don't think they will make it through the winter outside.