Always wanted to grow tall ferns but never tried it. Are there any taller ferns than ostrich for zone 6?
Some others come close (like royal, cinnamon and interrupted) but ostrich is the tallest that I have seen. Found a patch the other day by the side of a stream that were at least 6 feet tall.
Depends on site thou I think. Wet acidic site combined with some sun for those ferns to grow tall. Royal Fern reportedly can get quite tall, if you want a challenge.
Dixie Woodland Fern (Dryopteris) seems like the easiest fern to grow tall. I have fronds standing 42" tall on the north side of the house, and they last all summer til winter weather knocks them down, still green.