The hibiscus, or shoe flower, is a very common flower here in Kerala. Most houses will have a plant or two, and people will use these flowers as an offering in their daily worship. Notice I didn't make any mention of the religious affiliations of these houses, simply because I have seen these flowers being made offerings of in churches too. So, it's not just a Hindu thing. Apart from obvious conceptual human folly, this flower is beautiful in its simplicity, as you can plainly see.
Perhaps another point of interest surrounding this flower is the fact that they are very much part of Polynesian culture. When I was in Hawai'i, I noticed that the predominant motif in most examples of printed Aloha-wear was the hibiscus. More interesting than this perhaps, is the fact that of the various human migration patterns that existed among early human beings, one path seems to lead down the West coast of India, to the cape, across South Asia, and on to the islands that comprise Polynesia. Is it possible that this flower was taken along, whether inadvertently or not, by these people? Or was it already abundant all across this latitude? It just struck me as being too much of a coincidence that I could go from Kerala to Hawai'i and find such a specific similarity in preference.