There are hundreds to thousands of Hibiscus cultivars.
Most are cultivars of Hibiscus rosa-sinensis (red flowers) with other common parents being
Hibiscus schizopetalus (twisted red petals and long stamens and style), Hibiscus syriacus (bluish flowers),
Hibiscus moscheutos (very large white or pink flowers up to 20 cm across) and Hibiscus arnottianus
(tall plants with white flowers and red stamens).
Some cultivars are seen under different names.
Many with different names look very similar and it takes a real expert to identify them.
The following are a few distinctive ones and some named specimens.