'Really ferny...'? I suspect what you mean is really tree ferny, yes?! Investigate Blechnum gibbum - diminutive tree fern that just about cuts it as a houseplant (must be planted in ACIDIC ericaceous compost and watered with non-alkaline filtered tapwater). Plus, some of the other mini-trunked Blechnum species - search out a mail-order nursery and maybe buy a few cheap baby plants from a range of trunk-forming Blechnum species...B.minus, B.nudum, B.brasiliense, B.tabulare, etc. In the same trunky caudex style, I also like Polystchum proliferum, Asplenium nidus and A.bulbiferum - they don't need ericaceous treatment, though.

North-facing windows are a bit too dark - but you can always supplement them with a suspended double-tube growlight fixture, or something even more sophisticated from the kind of hardware employed by indoor hydroponic growers.

Steve - Brighton, Sussex Coast, UK

By fert I mean having pinnate or bi-pinnate fronds rather than those of Asplenium etc.
Gro lights arent really an option, and I think that windwsill is more north-west-quite bright-i have an indoor bonsai doing well on there already.
I tell you what tho, I'm curious as to what that mini-tree fern you mentioned looked like!
Going to google Blechnum gibbum now!

All my suggestions (except A.nidus, though it's still a formidable mini-trunked fern if you let it get big enough) were pinnate or bi-pinnate.

Steve

Blechnum gibbum, that dwarf tree fern I mentioned, is a bit of a well-kept secret. It's easily available on the high street (usually mislabelled) as a bland-looking baby pot fern and is incredibly cheap - almost at throwaway prices. Yet you'll never meet a florist who knows it's actually a proper little tree fern. Given the right care - acid compost and filtered non-limey water - they probably count as the ONLY tree fern species out there that can just about cut it as a houseplant. Not sure abut the north-facing window - a conservatory is probably the right location. But yes, do check this species out.

Steve

Sounds good to me! I noticed some small ferns in the veg shop in the village, but I'm not sure if theyre indoor or outdoor-and they usually dont know their plants either!