In the September 22nd post on this blog we featured a number of "Hardy Hibiscus". You may check that out by checking the archives on the right hand side of this blog.
Here is a picture taken yesterday of our Master Gardener holding two blooms from her tropical hibiscus "Jaz." This plant was recently moved into the greenhouse and should continue providing such blooms for some time.
Other interesting tropicals, but not ours.
This site has a great deal of useful information but the comments about identifying hardy vs. tropical may not be too helpful. http://www.trop-hibiscus.com/gindr.html
Garden centers tend to group all hibiscus together. You can tell if yours is probably a tropical if it has glossy, deep green leaves rather than the dull, medium green, heart shaped leaves of the hardy variety. However, there are several hundred varieties of hibiscus and they are easily crossed with one another. To further muddy the issue, the "Rose of Sharon" varieties tend to be hardy, but can have the double flowers, colors and deep green leaves of the tropicals.