nostr:npub1lfksuqx80mwp39q9dtk6jcgpf8kza4g6uc0qxqes05nmlt7fcr4qurxdx3 climate zones refer to the coldest possible temperature in winter. Some plants cannot survive deep freezes. I checked and Boston is between 6b and 7a depending on where you are. 

The east coast of US has milder winters than further inland and the PNW, so growing in zone 7 in Washington state is not the same as growing in zone 7 in Washington DC.