Polystichum munitum, the western swordfern, is an evergreen perennial fern native to western North America, where it is one of the most abundant ferns in forested areas. It occurs along the Pacific coast from southeastern Alaska to southern California, and also inland east to southeastern British Columbia, northern Idaho and western Montana, with disjunctive populations in northern British Columbia, Canada; the Black Hills in South Dakota, United States; and Guadalupe Island off of Baja California, Mexico. Western swordfern is known to have locally naturalized in parts of Great Britain and Ireland. Description The dark green fronds of this fern grow tall, in a tight clump spreading out radially from a round base. They are single-pinnate, with the pinnae alternating on the stalk. Each pinna is long, with a small upward-pointing lobe (a sword hilt, hence the name) at the base, and the edges are serrated with bristly tips. Individual fronds live for 1.5 to 2.5 years and remain attached to the rhizome after withering. The round sori occupy two rows on either side of the midrib of each pinna and are covered by a centrally-attached, umbrella-like indusium with fringed edges. They produce light yellow spores. In deep shade, fronds spread nearly horizontally but with increasing sun exposure grow more upright. Habitat and cultivation The preferred habitat of this fern is the understory of moist coniferous woodlands at low elevations. It grows best in well-drained acidic soil of rich humus and small stones. It is very resilient and survives occasional droughts, but flourishes only with consistent moisture and it prefers cool weather. In cultivation, it also responds well to regular, light fertilization. While this fern is a favored horticultural subject in western North America, it has proved difficult or impossible to cultivate satisfactorily in the eastern part of the continent. In the United Kingdom Polystichum munitum has gained the Royal Horticultural Society's Award of Garden Merit. Phylogeny According to a molecular phylogeny of Polystichum ferns based on plastid DNA sequences, P. munitum is most closely related to other North American Polystichum species, including the western species Polystichum lemmonii, Polystichum scopulinum, and Polystichum dudleyi, and the eastern species Polystichum acrostichoides. Utility The Coast Salish people of B.C. and Washington state use this plant as a pain reliever. When applied directly to the area where pain and inflammation occur, according to Della Rice Sylvester, an elder and medicine woman of the Cowichan tribe,