Answer: The tropical hibiscus (H. rosa sinensis) can be saved from year to year if you have the right place to keep it during the winter. (A greenhouse would be ideal.)
To keep it as a house plant, provide very bright light and ample humidity along with good air circulation. An average to cool room temperature is good, but protect it from hot or cold drafts. Bring them inside before temperatures drop below 50 to 55 degrees so they stay actively growing. They may drop some leaves when brought indoors while they acclimate to the lower indoor light conditions of winter.
The other option is to leave them outside a little longer in the fall until temperatures are in the upper 40's to 50 degrees so they begin to slow their growth. Then bring them into a cool location (temperatures about 45 degrees) and allow to rest for the winter. They can be kept in the light or in a shed or basement, for example. Water just enough to keep the soil from drying out completely. In spring, bring them into warmth and bright light and grandually increase water and fertilizer as they begin to grow.
If you are able to bring them inside at night to protect them from chilly nights, then set them outside to stay in the sun on mild days, that helps extend the season in both spring and fall. The longer they can be outdoors, the better.
I hope this helps.
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