I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
There are two common types or groups of hibiscus you may be referring to, the Chinese hibiscus (Hibiscus rosa-sinensis) or one of the perennial types (Hibiscus moscheutos, H. coccineus and others). Tropical types will need to be brought indoors before the first light frost. They are not cold hardy in your area. Perennial types should be cold hardy in some winters but may need a deep (6-8 inches) mulch to protect them in other, unusually cold winters. This also depends on the specific species you might have.
The key to great bloomin' hibiscus plants are to give them full sunlight and to keep them moist, but not soggy wet. Feed them enough to keep them vigorous with a complete plant food. Basically, hibiscus needs a significant amount of potassium (the 3rd number on a fertilizer label), a small amount of phosphorus (the 2nd number), and a moderate amount of nitrogen (the 1st number).
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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