Common Fern and Fern-Ally Species of the Northwest Forest






Terminology | Pictorial

Osmunda claytoniana
Interrupted Fern
Osmundaceae (Royal Fern Family)

Interrrupted Fern Description

General - large deciduous fern distinguished from other ferns by its large size and the spore bearing leaflets growing in the middle of the twice cut sterile fronds.

Leaves - spread from a central point, sterile fronds arch prominently outward, fertile fronds taller than the sterile ones; blade nearly twice-divided with leaflets deeply cut into crowded lobes; fertile blades have 2-4 middle pairs of leaflets transposed by much reduced fertile leaflets covered with brown spore cases; leafstalk smooth, green and thick.

Spore Clusters - spores formed on a modified frond; spore-bearing leaflets grow in the middle of the sterile fronds.


Damp fields or woods, in rich, often fine-grained, neutral or somewhat acid, soils throughout northwestern Ontario's boreal region and west to the prairies.


Economically, the roots and rhizomes of Osmunda species are the source of a fibre (osmundine, or Osmunda fibre) used as a growing medium for orchids and other epiphytes. The interrupted fern is popular as a greenhouse plant.

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