I hate to put a dampner on it but I nearly lost one planted in the ground the last cold winter we had. I live on the Glos Hrfd Welsh border so fairly well south It got caught by the weather and looked dead. I cut it down low, fed it and then it re-grew. Therefore, if you can sink the pot in the ground and, if you hear of really cold frosty/snowy weather then cover with fleece. I have just read Pete's message above and if you follow that you should be OK.