Look at your hibiscus’ leaves and flowers. If the leaves are dark green and glossy, you’ve got a tropical hibiscus. Flower color is another good clue. If the flowers are peach, orange, salmon, yellow or a tie-dyed stunner, it’s a tropical variety.  Colors like red, white and pink are common for hardy types.  Kansas State Research and Extension has some great information on hardy vs. tropical hibiscus.