The hardy hibiscus really don't need too much overwinter care. I am in northern ohio and have had temps as low as -10 without trouble. Just let them die back to the ground in the cooler weather. I normally cut the woody stems all the way to the ground after the leaves drop. You can mulch over top of the cut stems. They will sprout new growth in the spring. After a few years you will notice that the hibiscus may have out grown the area you have it planted in and may want to divide it. Do this in the spring and you will get a hibiscus that will grow to about 1/2 the height you have had the previous year. I did this in the spring and was very happy with the results. I received a total of 3 plants from the one and gave 2 away.

Enjoy them!
Tracy

Thank you for your reply and your answer to my question,
I really do appreciate it!

Good luck and enjoy the blooms. One more thing is that they do drop seeds quite a bit. You may notice some sprouts showing up below your hib next year. I had 2 dozen this year. I removed them and gave some away and planted others in different parts of the yard. If you don't want it to drop seeds then just pinch off where the spent flowers were. Enjoy!
Tracy