Polystichum munitumWestern Sword Fern
Western sword fern thrives as an understory plant in the deep shade of redwood forests, forming huge clumps six feet high in the moist, acid soil. It is an enchanting sight to see sunlight filtering through the branches of these enormous trees, spotlighting the brilliant green of the sword ferns below. Ferns and fern allies are descendants of a prehistoric class of plants that dominated the carboniferous period roughly 360 million years ago, when the great coal deposits of the world were formed.
One of the most familiar evergreen ferns of the West, sword ferns can be found from Alaska to Baja, and as far east as western Montana. There can be up to 75 to 100 fronds – a single divided leaf – growing in a clump. Each frond is compound, divided into separate leaflets called pinna or pinnae, which run alternately up the stalk. The pinnae are bristly and serrated and have a distinctive looking "hilt" at their base resembling the base of a sword. Young fronds, yet unfurled, are called "fiddleheads."
Ferns can often be identified by the distribution and shape of the tiny sori, or spore clusters on the undersides. Sori contain spores, and on sword ferns they are round and form two rows on either side of the mid-rib of the frond. Ferns also reproduce vegetatively by the branching of their understory rhizomes. Take a walk on the Redwood Trail and you will find sword ferns at every turn.
||Best in a shady, cool, humid environment with well drained soil; grows to 3 feet tall by 8 feet wide
||Sori (spore clusters) in 2 rows along underside of leaflet
||Plant around rocks or in a woodland setting, also works well as a potted plant, in a border or background plant
||Poly comes from the Greek word 'many' and shichos meaning 'row' refers to the sori arrangement under each leaflet. The word munitus, meaning protected, most likely refers to the indusium (covering) over the sorus.
A thorough and well-produced video on the fern lifecycle
IN BLOOM CONTRIBUTORS:
Photos by Docent Joanne Taylor; text by Docent Kathy McNeil; profile by Associate Curator David Kruse-Pickler.