Answer: If your hibiscus is Hibiscus syriacus (Rose of Sharon) rather than the tropical hibiscus, it will winter over in your zone 6B garden without problem. If it is the tropical hibiscus, plan on wintering it over indoors. Japanese Cleyera is rated hardy to your zone however you may want to provide some winter protection the first year. Simply mound some straw over the top of the plant, or use pine boughs, etc. to protect it from hard freezes. Once it is established it should be able to survive all but the most unusual winter weather. Allamanda (Allamanda cathartica) is a tropical plant and will show damage when temperatures dip below 30F. Again, you can either take the plant indoors for the winter or you can provide some frost protection out in the garden during the coldest nights.
Best wishes with your new plants!
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