Lykkefund is probably one of the hardiest white rambler. I grow it in Zone 5a, but against a wall so it would be safe to say 5b, and never had any die-back or frost damage. Even when we have, as we seem to have more and more, "unstable winters" with rather hot periods (around +8) followed by sudden cold periods, it doesn't seem to mind at all! In fact, opposite to a lot of multiflora ramblers that can be very hardy but start growing very early, sometimes even in the middle of the winter if we have one of those "hot periods", and the get frost nipped in the spring, Lykkefund stays dormant until quite late and i have never seen, over 8 or something years that i've been growing eat, any spring freeze damage.