About Polystichum munitum (Kaulf.) C.Presl
This fern, scientifically known as Polystichum munitum (Kaulf.) C.Presl, produces dark green fronds that grow 50 to 180 centimetres (1.6 to 5.9 ft) tall. The fronds form a tight clump that spreads radially out from a round base, and they are single-pinnate, with pinnae alternating along the stalk. Each pinna measures 1 to 15 centimetres (0.39 to 5.91 in) long, and has a small upward-pointing lobe at its base that resembles a sword hilt, which gives the species its common name. The edges of each pinna are serrated, and each serration ends in a bristly tip. Outside of the upward-pointing base lobe, pinnae are broadly linear in shape. They usually taper gradually and curve slightly toward the distal end of the frond. Individual fronds live for 1.5 to 2.5 years, and stay attached to the rhizome even after they wither. When new fronds emerge in spring, they are doubled back on themselves, and only the tip is circinate (rolled up). Round sori form in two rows on either side of the midrib of each pinna. Each sorus is covered by a centrally-attached, umbrella-like indusium with fringed edges, and the sori produce light yellow spores. Fronds grow nearly horizontally when growing in deep shade, but become more upright with increased sun exposure. Young plants often have paler green fronds and shorter pinnae. This fern’s preferred natural habitat is the understory of moist coniferous woodlands at low elevations. It grows best in well-drained acidic soil that is rich in humus and contains small stones. It is very resilient and can survive occasional droughts, but only flourishes with consistent moisture, and prefers cool weather. In cultivation, it grows well with regular, light fertilization. Though this fern is a popular horticultural plant in western North America, it has proven difficult or impossible to grow successfully in eastern North America. In the United Kingdom, Polystichum munitum has received the Royal Horticultural Society's Award of Garden Merit.
