Many of the following sites refer to more than one aspect of hibiscus care.
Q and A, CARE, TIPS, TROUBLESHOOTING
Plant and Pest Diagnostic Laboratory at Purdue University
University of Kentucky
WINTERISING - POTS
WINTERISING - GROUND
the following is from this site-
FREEZE AND WIND DAMAGE
Hibiscus are tropical plants and do not tolerate cold weather. Well watered and fertilized plants will fare better. Blankets, cardboard or a thick layer of mulch or straw will help. Do not spray to ice over the plants as they will kill them. Plastic, while better than nothing, is poor protection. Do not prune until Spring and prune into living tissue.