Certified GKH Gardening Expert
The tropical varieties must be growin in containers and overwintered indoors. These plants will not tolerate more than a night or two of light freezes. Even one hard freeze (below 25) could kill the plant. The hardy varieties don't need any special treatment and are hardy to Zone 5.
If the hibiscus has glossy, deep green leaves and 3-6" flowers of red, pink, orange, peach, yellow, or salmon, it is probably a TROPICAL hibiscus. Another way to check is if the blooms are double flowered, then you probably have a TROPICAL hibiscus. Hardy hibiscus do not come in these colors or in doubles! If the hibiscus has dull, medium green heart-shaped leaves, dinner plate sized white, pink or red flowers with HUGE, bomb shaped buds (2-4" in length!), it is a perennial, hardy hibiscus.