Answer: Tropical hibiscus (Hibiscus rosa-sinensis) really needs lots of sun to do well, preferably full sun all day long or at least six hours a day including the noon hour. Too much shade, cold drafts, cool temperatures below 55 degrees, or overwatering can all cause yellowing and foliage drop as well. Also check for insect problems such as whitefly or scale, these can cause yellowing. Finally, sometimes the oldest foliage will drop as the new growth becomes more active in the spring. I hope this helps you troubleshoot.
Q&A Library Searching Tips