Polystichum munitum (Western Sword Fern)

This fern is ubiquitous in conifer forests of western North America. So common, in fact, that it was one of only two ferns that I could identify for the first 56 years of my life (the other being Maidenhair Fern). I have been reluctant to post a profile of this because everybody knows what it is. But it grows on The Cliff, and more to the point, I recently found a related species that I hope to profile tomorrow, and this gives a comparison.

Young Western Sword Fern growing from a crack in a rock face.

Description– Dark green, single pinnate fronds that grow up to 5’ long, and issue from a central base. The pinnae are sharply but shallowly toothed, and have a small pedicle attaching them to the stem (rachis).

Similar species– Deer Fern and Licorice Fern have sessile pinnae. Polystichum imbricans has shorter, broader pinnae with pointed (apiculate) teeth. P. lonchitis has broader, spaced teeth, and grows in the subalpine and alpine zones.

Habitat– Damp conifer forests and forest edges.

Range– Region wide in appropriate habitat.

Reproductive timing– Mid summer

Eaten by– This is the preferred host plant of the moth Thallophaga taylorata.

Etymology of names– Poly- is from the Greek for many, and –stichum is Greek for rows, referring to the regular rows of sori. The species epithet munitum is Latin for ‘fortify’ and probably refers to the dense stands that this fern produces in good habitat.