I always assumed that Rigartoni was hardy- mine certainly coped ok last yr in a border in NWest.
I often grow hardy varieties in large pots on the patio, taking cuttings as routine in late summer. Sometimes those pot plants survive without being wrapped- pots very large & by a sheltered wall. The ones actually in the borders tend to be later in restarting in the following spring, but they will often continue flowering after the pot grown ones have been caught by the first frosts. J.