I heartily recommend hardy hibiscus, as they match your requirements and bloom beautifully.
Swamp hibiscus (Hibiscus coccineus) The leaf looks like Cannabis, the flower is georgeous red.
Hibiscus Rosemallow, "dinnerplate hibiscus" (Hibiscus moscheutos) Huge flowers, many colors available.
Confederate Rose (Hibiscus mutabilis) Grows large, double flowered.