Looking for a self-spreading outdoor fern....

I live in Zone 5 as well and though I dont have any suggestions..check this place out for Zone 5 ferns.... http://michiganbulb.com/ and come to think of it...thats a great idea actually...we have a ton of woods on our property and ferns would be a nice addition once we get them thinned out a bit (the ppl who owned this place before us didnt really take care of the property so we've been spending the past 3 summers getting it back on track)...