Regularity: Regularly occurring
Regularity: Regularly occurring
Western sword fern grows along the west coast from southeastern Alaska
to Santa Barbara County, California, and eastward through Washington and
northern Idaho into northwest Montana [39,40,69]. Disjunct populations
have been found in South Dakota and on Guadalupe Island off Baja
California [41,69,78]. In British Columbia, it is common west of the
Coast Mountains and on the Queen Charlotte Islands .
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
8 Northern Rocky Mountains
Occurrence in North America
Western sword fern is a relatively large, evergreen, long-lived fern
with long fronds arching from a short, scaly, erect rhizome [39,63,69].
The sword-shaped fronds are from 20 to 72 inches long (50-180 cm) and
divided pinnately . Individual fronds live for several years and
remain attached to the rhizome after withering . The largest
leaflets or pinnae are 1.2 to 16 inches long (3-15 cm). Spores are
borne in clusters called sori that are found between the midline and the
edge of the middle and upper pinnae [39,69].
Amount of light received influences western sword fern form. Following
disturbance that removes the overstory or when plants occasionally
establish on rocky outcrops at high elevations, the fronds are dwarfed
and more erect. This sun form of western swordfern also has pinnae that
are crisped and crowded so that they overlap and appear imbricated.
When shaded again, these plants return to normal form .
In southwestern British Columbia the rhizomes of western sword fern were
found to be vesicular-arbuscular mycorrhizal, although some plants have
been found with nonmycorrhizal rhizomes .
Catalog Number: US 279439
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Preparation: Pressed specimen
Collector(s): A. W. Anthony
Year Collected: 1896
Locality: Island off the coast of lower California & on adjacent mainland., Guadaloupe Island, Mexico, Central America
- Type collection: Maxon, W. R. 1903. Fern Bull. 11: 39.
Light and water relations: Western sword fern is found growing in shade
or in small openings within moist coniferous forests, while the
morphologically similar imbricated sword fern is found in distinctly
drier habitats, including rock crevices and dry coniferous forests
[39,69]. Western sword fern can survive very little moisture stress,
and thus in places on Vancouver Island where summer moisture deficits
are common, it is found only where seepage aguments the soil moisture
. It may indicate a high water table in northwestern Oregon .
Western sword fern is a minor species in Oregon riparian communities.
Its frequency is greatest in outer edges of riparian zones .
An ecological study of the coastal redwood (Sequoia sempervirens) region
grouped species along environmental gradients of moisture, nutrients,
light, and temperature. Western sword fern's distribution placed it in
the moderately moist to moist class. It had a low to moderate nutrient
requirement. Its ecological optimum light requirement was less than 3
percent, but it grew in areas having up to 40 percent of full sunlight
on a logarithmic light intensity scale .
Soils: In the Siskiyou Mountains of California, western sword fern is
an important mesic species found primarily on soils formed from quartz
diorite. Although a few plants are found in submesic conditions on
soils formed from olivine grabbro, imbricated sword fern is more common
on grabbro, and the only sword fern found on serpentine parent materials
. In British Columbia western sword fern grows on a variety of
parent material but prefers deep, loamy soils derived from fluvial
parent materials. It also prefers nutrient-rich soils and can be an
indicator of such soils when it is abundant and vigorous . Soils of
most sites in coastal Oregon where western sword fern is dominant are
deep and formed from sandstone and siltstone .
Elevation: Western sword fern grows from sea level to mid-elevations in
the mountains throughout its range . Its elevational limit in
Montana is 3,000 feet (914 m). In California it is usually found below
2,500 feet (762 m) . In coastal Oregon it is found below 1,700 feet
(518 m) .
Common associates: Associated understory species include salal
(Gaultheria shallon), salmonberry (Rubus spectabilis), thimbleberry (R.
parviflorus), vine maple (Acer circinatum), Oregon-grape (Mahonia
nervosa), twinflower (Linnaea borealis), oxalis, false
lily-of-the-valley (Maianthemum dilatatum), western springbeauty (Montia
sibirica), threeleaf foamflower (Tiarella trifoliata), evergreen violet
(Viola sempervirens), pioneer violet (V. glabella), red huckleberry
(Vaccinium parvifolium), evergreen huckleberry (V. ovatum), and rusty
menziesia (Menziesia ferruginea) .
Key Plant Community Associations
Western sword fern frequently indicates productive, moist forest habitat
types [18,27,33,37]. It may also indicate deep soils . Western
swordfern is an indicator of high quality sites for black cottonwood
(Populus trichocarpa)  and Douglas-fir (Pseudotsuga menziesii) .
Published classification schemes listing western sword fern as an
indicator species or as a dominant part of vegetation are presented
Forest types of the North Cascades National Park Service Complex 
Plant communities and environmental interrelationships in a portion of
the Tillamook Burn, northwestern Oregon 
Synecological features of a natural headland prairie on the Oregon coast 
Classification of montane forest community types in the Cedar River
drainage of western Washington 
A preliminary classification of the forest communities in the central
portion of the western Cascades in Oregon 
Natural vegetation of Oregon and Washington 
Ecoclass coding system for the Pacific Northwest plant associations 
Plant association and management guide for the western hemlock zone: Mt.
Hood National Forest 
Vegetation mapping and community description of a small western Cascade
Plant association and management guide: Willamette National Forest 
Forest ecosystems of Mount Rainier National Park 
The Quercus garryana forests of the Willamette Valley, Oregon .
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES22 Western white pine
FRES23 Fir - spruce
FRES24 Hemlock - Sitka spruce
FRES28 Western hardwoods
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
211 White fir
212 Western larch
213 Grand fir
215 Western white pine
221 Red alder
222 Black cottonwood - willow
223 Sitka spruce
224 Western hemlock
225 Western hemlock - Sitka spruce
226 Coastal true fir - hemlock
227 Western redcedar - western hemlock
228 Western redcedar
229 Pacific Douglas-fir
230 Douglas-fir - western hemlock
231 Port Orford-cedar
233 Oregon white oak
234 Douglas-fir - tanoak - Pacific madrone
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K001 Spruce - cedar - hemlock forest
K002 Cedar - hemlock - Douglas-fir forest
K003 Silver fir - Douglas-fir forest
K004 Fir - hemlock forest
K005 Mixed conifer forest
K006 Redwood forest
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K014 Grand fir - Douglas-fir forest
K025 Alder - ash forest
K026 Oregon oakwoods
K029 California mixed evergreen forest
Fire Management Considerations
On highly productive sites where competition from western sword fern
delays tree seedling establishment, slash burning and prompt forest
regeneration allow tree seedlings to establish before western sword fern
recovers . On sites where shrubs such as salmonberry are dominant,
clearcutting followed by slashburning, conifer planting, and release
treatments may convert the understory to western sword fern .
Plant Response to Fire
Recovery depends upon degree of fire severity. Morris  found that
western sword fern was equally adundant on burned and unburned sites
following slash burning in Washington and Oregon. A study in the
Tillamook Burn of northwestern Oregon, however, found frequency in
burned areas was about 2 percent, while frequency was 4 percent in the
unburned forest . On severely burned sites, western sword fern is
greatly reduced and recovers slowly over a period of 15 or more years
Immediate Effect of Fire
Fire top-kills western sword fern. It can survive intense fire [28,30],
but aboveground structures may lacking for several years afterwards
Rhizomatous herb, rhizome in soil
Initial-offsite colonizer (off-site, initial community)
Secondary colonizer - off-site seed
Western sword fern has two postfire regeneration strategies. It sprouts
from its stout, woody rhizomes . Additionally, a single western
sword fern frond may produce millions of light wind-borne spores each
year, enabling the species to colonize burn sites [28,57].
Sites where western sword fern is a major understory species are
generally resistant to the effects of fire (Barnett 1984 unpub., cited
More info for the terms: climax, cover, fern, ferns, frequency, succession
Facultative Seral Species
The light wind-borne spores of ferns enable them to swiftly colonize new
sites ; however, western sword fern's ability to colonize appears
limited by its sensitivity to water stress . On Vancouver Island it
is not present during the pioneer stage of floodplain succession.
Establishment occurs only under the shelter of a red alder canopy, and
its frequency is greatest in the climax community . In the
Douglas-fir zone of the Oregon Coast Range, seral communities are
commonly dominated by red alder/western sword fern. These communities
may extend beyond the fog belt . On western Oregon red
alder/salmonberry sites, western sword fern is found throughout
successional communities but increases with time .
In the Coast Ranges of Oregon, western sword fern survives disturbances
and becomes an important part of the seral vegetation while in the
Cascade Range it is of minor importance in early succession . In
southwestern British Columbia forests, western sword fern is absent
immediately after disturbance but enters the stand within a few years.
It gradually becomes more dominant, regaining postdisturbance cover by
the sapling and pole stages . Western sword fern is a dominant
plant in initial communities after logging or burning of California
coastal redwood forests, and remains dominant throughout succession
. In the Olympic Mountains western sword fern colonizes recent
clearcuts but only takes its place as a principal understory species in
Douglas-fir forests when the stand is 300 years old or older . In
coastal southern Oregon western hemlock, Douglas-fir, and western
red-cedar forest with western swordfern-Oregon oxalis understories,
western sword fern is dominant throughout succession, but its cover is
lower in densely shaded, near-climax stands than at any other time .
Its greatest cover in such dense forests occurs in canopy gaps [6,65].
Regeneration of western sword fern is mostly sexual; however, only a few
small, juvenile plants are present in most populations . Ferns
begin to produce spores on a regular, yearly basis when they are between
1 and 5 years of age . From early to midsummer mature ferns produce
millions of light, wind-borne spores. Evergreen ferns such as western
sword fern may retain some spores over the winter which are released the
following spring. The dry spores are very resistant to extreme physical
conditions and may remain viable for 2 to 4 years, although their
viability and ability to germinate declines with age .
The most important factor in spore germination is sufficient moisture.
Temperatures between 59 and 86 degrees Fahrenheit (15-30 deg C) and a
slightly acid to neutral pH are generally best for germination .
Western sword fern is one of the few fern species which is capable of
germination in the dark, although germination is best in the light .
When spores germinate, they produce tiny, bisexual gamete-bearing plants
(gametophytes) that do not look like the spore-bearing plants. These
tiny plants have no vascular system and require very moist conditions in
order to survive and enable the sperm to swim to the egg. The
spore-bearing plant, which develops in place from the fertilized egg, is
initially dependent on the gametophyte but quickly becomes independent.
In many ferns the gamete-bearing plants are self-fertile, but
self-fertilization in western sword fern gemetophytes probably occurs
less than 4 percent of the time. Outcrossing results in high levels of
genetic variability within and between western sword fern populations
Vegetative reproduction of western sword fern is limited but can occur
through division of its perennial, woody rhizome . The rhizomes are
erect and do not spread, although they branch with age .
Growth Form (according to Raunkiær Life-form classification)
Life History and Behavior
Molecular Biology and Genetics
Barcode data: Polystichum munitum
Statistics of barcoding coverage: Polystichum munitum
Public Records: 4
Specimens with Barcodes: 7
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: NNR - Unranked
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Western sword fern is not generally considered a serious competitor for
conifers. However, in localized areas where it is particularly abundant
and vigorous, it can interfere with conifer regeneration and growth.
Reduction or removal of western sword fern may reduce competition for
moisture and light in these situations . In laboratory and field
trials, it did not allelopathically inhibit other plants .
In coastal Douglas-fir forests western sword fern cover is greatly
reduced by accumulations of heavy slash and soil disturbance during
logging [6,24]. Western sword fern dominated only undisturbed
microsites following clearcutting in western hemlock (Tsuga
heterophylla), Douglas-fir, and western red-cedar (Thuja plicata)
forests with western sword fern-Oregon oxalis (Oxalis oregana)
understories. On disturbed plots western sword fern cover was under 10
percent for the first 5 years and then began to increase. Following
burning, cover was reduced to 0.5 percent . In Sitka spruce (Picea
sitchensis)-hemlock (Tsuga spp.) forests, overall cover of western sword
fern generally increased on thinned plots .
Western sword fern is resistant to most herbicides, although its
response is intermediate to high glyphosate concentrations .
Western sword fern cover was reduced but still abundant following
various treatments in Oregon. The treatments included applications of
2,4,5-T and picloram followed by crushing in one area and burning in
another. It also recovered well following spraying with glyphosate;
however, it almost disappeared from plots that were severely scarified
. Dicamba and bromacil are effective herbicides on western sword
fern, although dicamba will cause injury to trees [49,67]. Late spring
is the most efficient time to treat it with dicamba, as twice as much
dicamba is needed in midsummer.
In Oregon presence of western sword fern is one of the indicators used
to predict the relative difficulty of conifer regeneration. A range of
1 to 14 has been developed, with higher values indicating better
regeneration. After clearcutting in Oregon, western sword fern presence
had an indicator value of 11, while after partial cuting its value was
2. This same scale is used to indicate relative temperature conditions
in undisturbed stands . In southwestern British Columbia western
sword fern is an indicator species in two associations used to estimate
Douglas-fir site index. These associations indicate moderately dry to
wet and generally nutrient-rich sites . In western hemlock forests
of Idaho's Clearwater National Forest, clusters of western sword fern or
patches of mixed ferns may indicate areas of excess soil moisture and/or
mass soil movement .
Relevance to Humans and Ecosystems
Other uses and values
Western sword fern is cultivated as an ornamental plant and is well
suited to a variety of garden situations. Its fronds are harvested in
quantity for florists to use as background greenery [19,40]. The fronds
are edible when very young .
Western sword fern has particularly high levels of potassium and
nitrogen when it occurs as an understory plant in seral red alder (Alnus
rubra) stands. Calcium, phosphorus, and magnesium levels are higher in
the understory of seral red alder stands than in the understory of
Douglas-fir stands [13,76].
The palatability of western sword fern is rated as fair for Roosevelt elk
on the Olympic Peninsula of Washington .
Importance to Livestock and Wildlife
Wildlife: Western sword fern provides forage for elk, deer, and black
bear . In coastal Oregon forests it is one of the ten most
frequently used foods of Roosevelt elk [6,24]. On the Olympic peninsula
of Washington, the fronds are eaten yearlong and are of medium
importance to Roosevelt elk. Its use is moderately heavy in winter when
snow depth permits grazing. In one study, it was found in eight of nine
Roosevelt elk stomachs sampled and accounted for 9.2 percent of the
total food volume eaten . In Oregon western sword fern is a
preferred food of mountain beaver .
Livestock: Ferns are a very minor part ( less than 2%) of sheep diets in western
|This article needs additional citations for verification. (April 2014)|
Polystichum munitum (western sword fern) is an evergreen fern native to western North America, where it is one of the most abundant ferns. 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 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 50 to 180 centimetres (1.6 to 5.9 ft) 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 to 15 centimetres (0.39 to 5.91 in) long, with a small upward-pointing lobe 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.
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.
While this fern is a favored horticultural subject in western North America, it has been found to be difficult or impossible to grow satisfactorily in the eastern part of the continent.
Traditional food usage
Western sword fern spores have many medicinal uses, including relieving the pain from the sting of a stinging nettle. It is also commonly used by florists as an ornamental plant.
- Paul Alaback, Joe Antos, Trevor Goward, Ken Lertzman, Andy MacKinnon, Jim Pojar, Rosamund Pojar, Andrew Reed, Nancy Turner, Dale Vitt (2004). Jim Pojar and Andy MacKinnon, ed. Plants of the Pacific Northwest Coast (Revised ed.). Vancouver, British Columbia: Lone Pine Publishing. p. 53. ISBN 978-1-55105-530-5.
Polystichum munitum appears to be most closely related to P . imbricans based on morphologic (D. H. Wagner 1979) and electrophoretic (P. S. Soltis et al. 1990) analyses. The chloroplast DNA of P . imbricans , however, is divergent (G. Yatskievych et al. 1988), suggesting a chloroplast origin independent of the nuclear genome. That Polystichum munitum is related to P . acrostichoides is supported by data from chloroplast DNA analysis (G. Yatskievych et al. 1988) but contradicted by data from electrophoretic studies (P. S. Soltis et al. 1990).
Polystichum munitum can be distinguished from P . imbricans by its persistent, wide (the largest wider than 1 mm) distal petiolar scales; such scales of P . imbricans are less than 1 mm wide and fall off early.
From an evolutionary standpoint, Polystichum munitum is a diploid progenitor of P . andersonii , P . californicum , P . setigerum , and, perhaps, P . scopulinum . Hybrids with all except P . setigerum have been reported, all triploid, attesting to its parental role in the tetraploids (see discussion under each). Hybrids with P . braunii (A. Sleep and T. Reichstein 1967), P . kruckebergii (P. S. Soltis et al. 1987), P . dudleyi (W. H. Wagner Jr. 1973), and P . lemmonii (P. S. Soltis et al. 1989) also have been reported.
The population on Guadalupe Island has been called Polystichum solitarium Maxon.
Names and Taxonomy
western sword fern
sword holly fern
The currently accepted name of western sword fern is Polystichum munitum
(Kaulf.) C. Presl. There are no infrataxa .
Sword fern outcrosses frequently and hybrids have been identified from
crosses with Anderson holly fern (P. andersonii) [64,69], Eaton holly
fern (P. scopulinum) , California holly fern (P. californicum),
Shasta fern (P. lemmonii) , and imbricated sword fern (P. imbricans)
. Imbricated sword fern and western sword fern are morpholigically
similar, but are considered separate species [74,78].
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