There are 62 species of ferns and their allies in Glacier National Park. Most are found in partial shade and wet conditions common to the lush west-side cedar-hemlock forests. In drier forest openings, bracken fern grows in abundance on poor soils. It grows 2 - 4 feet tall on a single stalk that flattens horizontally. It is one of the first plants to die during frost, but remains upright (and colorful) for a few days.  Bracken fern's scientific name, Pteridium aquilinum, suggests it appeared to the author as the wing of an eagle. At a few locations in the park, hikers may see a triangular-looking fern hanging from moist cliffs. This is beech fern, common in the east, but probably the rarest fern in the park.

Moonwort ferns are very small and have a single leaf and a single fertile spike. Moonworts produces spores which disperse through the soil instead of the air and water like most ferns.  Because the spores don't travel long distances, the various species frequently hybridize and often form fertile hybrids which become new species.  A new species of moonwort fern recently discovered in Glacier Park is currently being described. Club mosses are small, ground-cover variants of ferns which display a greenish "club" spore capsule. Native people used the spores as a blood-clotting agent and wound dressing, and occasionally threw it into fires as "flash-powder" for special effects during ceremonies. Rough horsetail (scouring rush) grows as a single spike in wet areas. It has so much silica in the stem that it can be used as an abrasive scrubber. Horsetails are primitive plants which can be found in fossil records dating back over 300 million years.