Cutting to the crown wouldn't be possible for established plants growing in the ground though, because the crown is usually beneath the soil surface. Cutting the leaves a bit above the soil surface may not get rid of the rust unless the remainder of the leaves are killed by cold - cutting infected leaves causes spores to fall down between the leaf stumps where they could infect, and also pustules can exist not very far up from the crown.
It's not likely that the rust would winter over in Gerry's zone unless there were some specific circumstances, like possibly a heavy winter mulch that allows some leaf bases to stay green. Or maybe a very heavy winter snow before the plants have frozen back and which remains all winter. Those last two are speculation though, not something that we know happens for sure. A greenhouse would be risky though.
