Fertile leaflets are located partway up fronds.
Similar species: Cinnamon Fern (Osmundastrum cinnamomeum) - grows in wet areas; has downy stems near base; separate fertile frond; lacks the "interruption". Ostrich Fern (Matteuccia struthiopteris) - has separate fertile frond; all stems grow from a black knobby growth; lacks the "interruption". Marsh Fern (Thelypteris palustris) - crooked stem; lacks the "interruption".
1 m (2-4 ft)
Fertile leaflets partway up the frond - this is unique and distinctive.
A nice grove of Interrupted Fern in the forest. It's a real treat to come across such a large patch of this living fossil.
The fossil record for this species goes back 200 million years, making it the oldest known fern species still living in the world!
View from above of an Interrupted Fern. Note that all the fronds grow from one point.
Closeup view of a frond.
Closeup view of leaflets. Once you get to know this fern you will see that the shape of the leaflets is distinctive.
Underside of the frond.
Water beads up nicely on Interrupted Fern.
This photo also shows spent fertile leaflets.
Fronds unfurling in spring (late May). Note the fertile leaflets that "interrupt" the sequence of infertile (sterile) leaflets along the stem.
Another view of an unfurling frond in late May. Note the interruption along the stem. The dark leaflets are the fertile ones, which "interrupt" the fertile ones. No other fern in Ontario is like this. However, not all Interrupted Ferns grow fertile leaflets in a given year.
Closeup view of young fertile leaflets.
Spent fertile leaflets in later summer (early September).