katy-
I am in Zone 9. My maidenhair fern over winters outside just fine-it dies back if it gets really cold but comes back. I have a bed of maidenhair fern that is in a sheltered area-faces west but grows against a north wall so doesnt get much sun. My potted fern in the backyard faces east and is close to the house. The coldest it has been here is about 30 degrees, a few dips in the 20s.
Its my favorite fern too, so I know how you feel about it.
Hope this helps.

I am in Zone 7 and have had a Maidenhair Fern to live through the past 2 winters in a container outside. The container is sitting on the ground under two oak trees. Temps have dropped into single digit temps.....though they haven't stayed that low very long.

Hope this helps.

Theo

In my zone 8b garden in Alabama, I have my maidenhair ferns in the ground. They die back but come out again early in the spring. I have mine in a full shade location, in a protected area behind a tall privacy fence. I always mulch with pine straw or loose leaves and pull that cover back in early spring.

I'm not familiar with the zone for Pac NoWest, but if it is anything like Seattle, you are not in the deep freeze winter area. If you choose to keep your fern in a container, be sure to surround the POT with protection for the root system, and then loosely cover the planted area as well.

Some ferns like dryness, instead of wetness, and I don't water my ferns in the winter...unless they are indoors. Root rot is a big problem, as you probably know.

Where I live in california, maidenhair ferns grow lithophytically near riversides and die back during the summer drought and come back in the fall when rain returns. I would assume that they can handle any winter you would have if they are hardy enough to withstand california drought with no soil, especially if people here say they have theirs outside in the cold. The worst that could happen is probably that it would lose its leaves and come back in a few months.

Where I live in california, maidenhair ferns grow lithophytically near riversides and die back during the summer drought and come back in the fall when rain returns. I would assume that they can handle any winter you would have if they are hardy enough to withstand california drought with no soil, especially if people here say they have theirs outside in the cold. The worst that could happen is probably that it would lose its leaves and come back in a few months.

I know that it is too late to make an answer...did your fern stay out or come in? There are over 700 kinds of maidenhair fern...I have 2 types outside and 3 kinds inside...makes a big difference to know what kind you have.

Yes as stated there are tropical and temperate species. I'm in zone 6b in Pennsylvania and only a few species will survive winters here. They are Adiantum hispidulum-native and venustum from China. Capillus-veneris and it's cultivars are hardy to zone 7.

Scott