Well there's alot more to it than zone... zone only formulates the lowest temperatures you'll likely see in the winter... how long it's that low and what the daytime temperatures might be during that time ... the amount of moisture ..wind are not considered in the zones... all of these can make or break your brugs.. microclime has everything to do with them surviving... being against a south wall is a great start... more so if it is a brick or block wall.. with an uninsulated foundation.. more so if it is also blocked on the sides with another wall .. or wind break.. perhaps where a dryer vent exits the house.. in front of windows on the south side is a help.. as the reflected light/warmth is a great boost to theground temperatures in front of them... like having a double sun.. and mulch.. not only on top of the plant... but feet thick for yards away from it... find out to what depth your ground will freeze to in the winter.. and have more mulch or dirt on top of them than that.. you might find you can get lucky.. and remove the mulch early.. cover the ground with plastic to heat it up in the spring.. it might be less work to dig them and water them all winter inside ..
