Answer: If the plant is a Hibiscus moscheutos such as one of the "Southern Belle" series or a "Lord Baltimore", you can plant it outside and it should be perennial for you. It will die back to the ground each winter and regrow from the roots beginning in very late spring.
Give it full sun and rich, evenly moist soil for best results. Also allow it plenty of room to grow over the coming years.
To plant it, dig a hole three times wider than the container and about as deep. Loosen any encircling roots and set the plant in the hole so it is at the same depth as it grew in the container. Replace the soil in the hole and water generously to settle any air pockets. Mulch with several inches of organic mulch spread in a flat layer over the root area. Water as needed to keep the soil evenly moist, meaning damp like a wrung out sponge. Next spring, top dress with compost and apply a general purpose granular fertilizer or a slow release granualar fertilizer such as 10-10-10 per the label directions.
If your plant is a tropical hibiscus or Hibiscus rosa-sinensis, you will have to bring it indoors as a houseplant for the winter if you want to keep it from year to year. If you plan on doing this, grow it as a container plant year round.
Water as needed to keep the soil evenly moist, and fertilize regularly with a water soluble fertilizer such as 10-10-10 plus minors. Or, use a slow release granular fertilizer per the label directions. Give it a spot with full sun all day. In the fall, when temperatures drop to 50 to 55 degrees, bring it indoors.
Good luck with your hibiscus!
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