Hi, How do the Cityline hydrangeas do in zone 5? I'm particularly interested in "Rio" (but would be happy with any of the others if they would fare better).
Cityline hydrangeas will need the same careful winter protection as any other hydrangea macrophylla in your zone, as well as a mulch to protect roots. I suspect it would be iffy in Z5. An alternative might be to grow it in a large container you could move to an unheated garage in winter, where you would still protect it (wrap) during the coldest of weather.