Answer: This plant, Hibiscus syriacus, is considered hardy into zone 5, but your zip code places you in zone 5A or the coldest part of zone 5. Depending on your microclimate, it may be as cold as zone 4 -- especially in a windy, exposed location. I am not sure if you will be able to overwinter this shrub successfully or not, but to give it the best chance I would suggest applying a heavy mulch in late fall (six inches deep over the entire root area but keep it several inches away from the trunk) and if at all possible, provide a wind break. (Maybe a burlap fence or a section of picket fence for example.) Snow is a good insulator so hope for snow, too. Do not prune it in the fall. If there is dieback over the winter, trim it off as far as necessary to remove the dead wood in the early spring, pull aside most of the mulch so the soil can warm up, and wait and see if it can regrow from the ground or old wood. This plant normally begins to grow very late in the spring so wait well into June before you give up. This plant grows quickly and blooms on new growth of the season, so it should still be able to bloom as long as it survives the winter. Since you will likely have substantial winter damage each year, I doubt you will be able to grow it as a tree form but it should be a large bush. Good luck with your rose of sharon!
Q&A Library Searching Tips