Western Sword Fern

Polystichum munitum
NATIVE

Description (Jepson, PlantID.net)

• Fern (Polypodiopsida)
  • Ferns are a group of vascular plants that produce spores (reproductive cells)
    • Produce no flowers or seeds
    • Fossil records date back almost 400 million years, versus 130 million years for flowering plants
• Wood Fern Family (Dryopteridaceae)
• Perennial herb
  • Grows from rhizomes (horizontal underground stems)
• Fronds
  • Lanceolate to narrowly-elliptic, up to 47 in. long, stiff
  • Compound (divided into leaflets), with 1 level of division (1-pinnate)
  • Serrated leaflets with bristly tips
    • Single upward-pointing lobe next to stem
  • Lower part of stalk (petiole) densely scaly
• Sori
  • Sori (singular: sorus) are clusters of spore-producing, sac-like structures called sporangia (singular: sporangium)
    • Sporangia sacs split open to catapult mature, microscopic spores, which are wind dispersed
  • Located on the underside of leaflets in parallel rows, either side of the midrib
  • Protected by a tissue flap called an indusium (plural: indusia) with irregular “hairy” edges
• Height to 4.5 ft.

Distribution

• Native to California
  • Mostly occurs as an understory plant in closed canopy woodlands
  • See Calflora for statewide observations of this plant
• Outside California, grows in Montana, South Dakota, Guadalupe Island, Mexico, and from the coastal ranges of Alaska south into California
• Grows at elevations to 5,250 ft.

Uses (San Mateo County Parks prohibits removal of any natural material)

• Wildlife (Verlande 2024)
  • Black-tailed deer (Odocoileus hemionus columbianus) are known to eat the fronds
  • Provides cover and nesting material for birds, small mammals, and deer
• Native people
  • Fronds used to line acorn-leaching basins and earth-baking ovens
  • Fronds also used as toys and decorations
  • Fronds used by Miwok to thatch roofs (Lightfoot 2009)
  • Fronds also used for bedding, headdresses, and various games by tribes north of California
  • Rhizomes peeled and eaten, boiled or baked in coals
• Commercially, plants are used in landscaping and floral arrangements

Name Derivation

• Polystichum (pol-ee-STY-kum) – from the Greek poly, “many,” and stichos,“row,” referring to rows of sori
• munitum (mew-NY-tum) – from the Latin for “armed” or “fortified”
• Sword – at the base of each leaf is a lobe that looks like the hilt of a sword

Notes

• One of the most abundant ferns in the Western flora and naturalized in Europe
• Watch this short video showing fern reproduction in action (KQED 2024)
• Western sword ferns, like most medium-sized forest ferns, begin making annual spores between 1 and 5 years of age
• Fresh, silky-haired, unfurling fronds are called fiddlenecks
• Individual fronds live for 1.5 to 2.5 yrs. and remain attached to the rhizome after withering

ID Tips

• Fronds are noticeably dark green and usually stiff
• Individual leaflet has a lobe (“sword hilt”) at the base
• Check out this short Jepson video for more ID tips

At Edgewood

• Found in well-shaded woodlands
  • Found off-trail above the picnic area and along the lower part of Old Stage Road
  • See iNaturalist for observations of this plant
• Grows new fronds for up to 10 months from the beginning of wet season; some fronds stay green all year

Specific References

Jepson Herbarium. 2019, Aug. 29. Polystichum munitum (Western sword fern) [Video]. The Jepson Videos: Visual Guide to the Plants of California. The Regents of the University of California. YouTube.

KQED San Francisco. 2024, April 16. Watch ferns get freaky [Video]. Deep Look. YouTube.

Verlande, S. 2024. Sword fern Polystichum munitum. North Creek Wetland. University of Washington, Bothell, Washington.

Zouhar, K. 2015. Polystichum munitum. Fire Effects Information System. United States Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

General References

Calflora Database. 2014. Berkeley, California.

Calscape. 2018. California Native Plant Society.

Charters, M.L. 2015. California Plant Names: Latin and Greek Meanings and Derivations.

Charters, M.L. 2017. Southern California Wildflowers: Guide to the Pronunciation of Specific, Generic and Family Names.

Corelli, T. 2004. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California.

Flora of North America. efloras.org.

Harris, J.G., and M.W. Harris. 2013. Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, Utah.

Lightfoot, K.G., and O. Parrish. 2009. California Indians and Their Environment. University of California Press, Berkeley, California.

Native American Ethnobotany DB.

Regents of the University of California. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.