This humongous six inch wide tropical hibiscus, Hibiscus rosa-sinensis, looks like it might be from Hawaii or Florida, but was actually found in K and K Nursery and Landscape of Norman, just south of Oklahoma City, where winter nights are already seriously cold by our coastal California standards. It is happy to bloom so impressively only because it is in a greenhouse. Even here in our pleasantly mild climates, tropical hibiscus are happiest where sheltered above from frost, by eaves or evergreen shade trees that are high enough to also allow warming sunlight through. In the cooler spots, even sheltered plants occasionally get damaged by frost, and need some time to regenerate after winter.
Some of the classic tropical hibiscus that typically have smaller flowers can grow above single story eaves if not pruned down. Most modern varieties with larger or ruffly double flowers rarely reach the eaves, and many stay less than six feet tall even without pruning. The evergreen foliage has an appealing glossy sheen, which is an ideal backdrop for the red, pink, white, yellow or orange flowers.