Tropical plants are those species native to the tropics. Strictly speaking, the Tropics, seated in the equatorial regions of the world, are limited in latitude approximately 23.4° N latitude, and 23.4° S latitude. In the USA, tropical flowers can be grown outdoor in mild climate such as Southern California or South Florida. But they need to be in greenhouse or kept indoor during winter in most of the states in the USA.
Here are some sample pictures of tropical flowers in these pages:
Search for a flower: