NPS/Bill Gawley

Visitors to Acadia National Park will find many ferns, an interesting group of spore-producing plants. They thrive in cool, moist, shaded areas, which are quite common on the coast of Maine.

Some of the easier-to-recognize ferns are species of rock polypody (Polypodium virginianum and P. appalachianum), which appear almost identical and are often found growing in leaf litter duff on top of large rocks. The fronds are singular and look like they are growing in a small colony or mat. If you turn one of the fronds over you may see the round sori, clusters of spore-producing structures, on the underside.

Another pair of related common ferns are cinnamon fern (Osmunda cinnamomea) and interrupted fern (Osmunda claytoniana). These two also look very much alike. Both are large ferns with non-fertile (vegetative) fronds arranged in whorls around the center. Cinnamon fern has separate, fertile, spore-producing fronds which sprout from the center of the plant in spring. These fronds are a cinnamon-like golden brown in color, which accounts for the plant's common name. Interrupted fern produces fertile leaflets in the upper third of the vegetative fronds, hence the frond is "interrupted" by the smaller fertile leaflets "within" the frond.