Two of my ferns are Ontario Natives and both are pretty well at their peak right now.
Adiantum pedatum (Maidenhair Fern)
Adiantum pedatum
Matteuccia struthiopteris (Ostrich Fern)
Both are easy to grow and really brighten up a shady area of the garden with their bright green colour. The Adiantum pedatum especially provides fantastic texture and movement as well.
All Andrew's Plants 
I just bought a baby Adiantum pedatum at the NANPS plant sale. Your colony looks amazing!
Thanks. I've had it for five or six years now, and moved it once two or three years ago. It's gotten to maybe 2.5-3' across? (there's some grass and a clover leaf at the bottom of the picture for scale)I've found it to be extremely easy, barely even needing to be tidied up in the spring and completely well behaved. For sure a favourite fern of mine.