Answer: I think you probably have the tropical hibiscus (Hibiscus rosa-sinensis) that are usually sold as patio plants. These are tropical plants and must be brought inside before temperatures drop below 50 degrees. (They love heat, humidity and sun and so actually do better if you can set them outside for the summer.) For this reason they are kept as container plants to make moving them easier -- and less stressful on the plants.
These plants can grow very leggy. To try to keep them more compact you will need to prune them. You can prune them back very hard in the fall when you bring them indoors (if you are pressed for space in a sunny window) or you can wait until late winter to do the hard pruning. They bloom on older wood, so this can delay the next bloom cycle until well into summer.
The other pruning option is to periodically prune out some of the longest growth, taking just a few branches at a time but doing a little pruning every other month or so. This ongoing process maximizes the bloom season but it is less useful in controlling the overall size of the plant.
I hope this helps.
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