Polystichum munitum
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| iWestern Sword Fern | ||||||||||||||
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 Polystichum munitum growing in the Columbia River gorge
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| Polystichum munitum (Kaulf.) C.Presl |
The Western Sword Fern (Polystichum munitum) is an evergreen fern native to western North America, where it is one of the most abundant ferns occurring along the Pacific coast from southeast Alaska south to southern California, and also inland east to southeastern British Columbia, northern Idaho and western Montana, with isolated populations in interior northern British Columbia, the Black Hills in South Dakota, and on Guadalupe Island off Baja California.
The dark green fronds of this fern grow to 50-180 cm 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 1-15 cm long, with a small upward-pointing lobe at the base, and the edges are serrated with bristly tips. Individual fronds live for 1.5-2.5 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.
The favored habitat of this fern is the understory of moist coniferous forests at low elevations. It grows best in a well-drained acidic soil of rich humus and small stones. Sword ferns are very tough, and can survive occasional dry periods, but do well only with consistent moisture, light sunlight, and prefer cool weather to overly warm. In cultivation, they also respond well to regular, light applications of fertilizer.
