Throughout much of its range it is the most common Cystopteris fern species.

[3][4] Unlike most species of the genus Cystopteris, this fern is exclusively terrestrial, often forming large, dense colonies.

Some fronds may remain by late summer, but most have disappeared.

[5] The specific name, protrusa, refers to the fact that the rhizome protrudes a short distance beyond the current year's fronds to form the following year's leaf buds.

Sori are round and covered in a bladder-like indusium.