United States

Department of

Agriculture

Forest Service

Alaska Region

R10-RG-182

June 2010

Ferns of the 

National Forests

in Alaska

Ferns of the 

National Forests
2 3

Ferns abound in Alaska’s two national forests, the Chugach 

and the Tongass, which are situated on the southcentral 

and southeastern coast respectively. These forests contain 

myriad habitats where ferns thrive. Most showy are the 

ferns occupying the forest floor of temperate rainforest 

habitats. However, ferns grow in nearly all non-forested 

habitats such as beach meadows, wet meadows, alpine 

meadows, high alpine, and talus slopes. The cool, wet 

climate highly influenced by the Pacific Ocean creates ideal 

growing conditions for ferns.

In the past, ferns had been loosely grouped with other 

spore-bearing vascular plants, often called “fern allies.” 

Recent genetic studies reveal surprises about the 

relationships among ferns and fern allies. First, ferns 

appear to be closely related to horsetails; in fact these 

plants are now grouped as ferns. Second, plants commonly 

called fern allies (club-mosses, spike-mosses and quillworts) 

are not at all related to the ferns. General relationships 

among members of the plant kingdom are shown in the 

diagram below.

Thirty of the fifty-four ferns and horsetails known to grow 

in Alaska’s national forests are described and pictured in 

this brochure. They are arranged in the same order as listed 

in the fern checklist presented on pages 26 and 27. 

Fern structure

Ferns and horsetails reproduce via spores instead of by 

seeds, and don’t have secondary growth, in other words, 

they do not make wood. 

Ferns generally have relatively large leaves (fronds), 

composed of a blade and petiole (leaf stalk). Frond shape, 

size, petiole length, texture and degree of leaf cutting vary 

considerably from species to species. In the spring, when 

new fronds emerge, they unroll. These unrolling fronds are 

commonly called fiddleheads.

Fern leaves

The blade may be variously divided into segments called 

pinnae; a single segment is a pinna. A pinna may be 

further divided; the smallest segments are called pinnules. 

Blades can be simple, where the blade is undivided (no 

ferns in Alaska have simple blades) or pinnate, where the 

blade is divided into segments completely separated from 

each other, e.g. green spleenwort (p. 15), deer fern (p. 19).

Parts of a fern frond, northern wood fern (p. 21). 

Midrib

Pinnule(s)

Pinna

Petiole

(leaf stalk)

Frond

(leaf)

Blade

Flowering 

Plants

Conifers

Mosses & 

Liverworts

Ferns & 

Horsetails

Club-mosses, 

Spike-mosses 

& Quillworts
4 5

Some ferns, such as the moonworts (p. 8-9), have modified 

leaf segments producing only sporangia. Deer fern (p. 19), 

parsley fern (p. 15) and ostrich fern (p. 21) bear two kinds 

of leaves; sterile leaves with no sporangia, as well as highly 

modified fertile leaves with sporangia. Ferns with two kinds 

of leaves are called dimorphic. 

Fern and Horestail reproduction

Ferns and horsetails have two free-living generations; a 

diploid sporophyte (spore-producing plant) and a haploid 

gametophyte (gamete-producing plant). Plants we see 

as ferns or horsetails are the sporophyte generation. The 

sporophyte generally releases spores in the summer. Spores 

must land on a suitable surface, such as a moist protected 

area to germinate and grow into gametophytes. 

The mature gametophyte 

of many of our ferns looks 

like a little flat green 

heart, about the size of a 

fingernail, as illustrated 

here. Male and female 

reproductive structures 

develop on the lower 

surface of the same, or 

more often, on different gametophyte plants. At sexual 

maturity the male structures release sperm that swim 

through the film of water of the moist habitat to fertilize 

the egg in the female structure. Horsetail gametophytes are 

similiar, but appear more like little green mounds.

Usually, many gametophytes grow in close proximity to 

each other, and in most ferns and horsetails the sperm of 

one gametophyte is most likely to fertilize the egg of a 

different gametophyte. This fertilized egg develops into an 

embryo, which is the beginning of the diploid sporophyte 

generation. The first tiny leaf of the sporophyte emerges 

from the bottom of the gametophyte (which disintegrates) 

and grows upward and soon becomes a plant we see as a 

fern or horsetail. 

Many ferns are known for their lacy appearance because 

the blades of these ferns are even further divided;

2-pinnate blades are divided two times and 3-pinnate

are blades divided three times. In most cases, the ultimate 

divisions (often called segments) don’t cut to the pinna 

axis, so the term pinnatifid is added to the degree of 

cutting to describe this type of blade dissection. Examples 

of various degrees of leaf divisions include pinnatepinnatifid, e.g. northern beech fern (p. 15) and 3-pinnatepinnatifid, e.g. western oak fern (p. 19).

Fern sori

Sori (singular = sorus) are groups of sporangia (singular = 

sporangium), which contain spores. Sori are usually found 

on the underside of the blade. Young sori are commonly 

covered by flaps of protective tissue called indusia

(singular = indusium). The shape and arrangement of the 

sori and indusia are often useful characters for identifying 

ferns. But, depending on the time of year, sori and indusia 

may not be useful characters because they may be too 

immature or too mature to reveal their diagnostic features.

Sorus Indusium Spore

Sporangium

Young

sporophyte

Gametophyte First root

Second

leaf

Stem apex

First leaf

Pinnate Pinnatifid 2-pinnate 2-pinnatifid Pinnate 2-Pinnate 2-Pinnate - 

pinnatified

Pinnate - 

pinnatified
6 7

Cone Branch

Leaf tips

Sheath of 

fused leaves

Joint

Stem

Fused leaves

Joint

Above-ground stem

Below-ground stem

Joints

Roots

Fern Stems and Roots

Fern stems (rhizomes) are inconspicuous because they 

generally grow on or below the surface of the substrate on 

which the fern grows. This substrate can be soil, moss or 

duff. Because the stems are in direct contact with the soil 

people often confuse stems with roots.

Stems can be short-creeping, with fronds that are 

somewhat scattered along the stem, such as the fragile fern 

(p. 17); stems can be long-creeping resulting in fronds 

scattered along the stem, exemplified by the licorice fern 

(below left). Stems can also be vertical, producing rosettes 

of leaves, as shown by the northern wood fern (below 

right), and as displayed by the sword ferns (p. 22-25).

Fern roots are generally thin and wiry in texture and grow 

along the stem. They absorb water and nutrients and help 

secure the fern to its substrate. 

Horsetail Structure

Horsetails have prominent stems and minute leaves. Leaves 

arise at the joints of the above-ground stem. Since the 

leaves are fused to each other around the stem, they form 

a sheath extending a short way up the stem from the joint. 

The color, number and leaf tip shape of these ensheathing 

leaves are good characters for distinguishing horsetails 

from each other (p. 10 and 11). Most horsetails also have 

slender, soft branches radiating from the joints. These 

branches give many horsetails their “horsetail” look.

The above-ground stem is vertically grooved and hollow. 

Silica is incorporated in the stem’s outside surface, giving 

horsetails their characteristic rough feel; in fact, they have 

been used as scouring pads. The underground stem is 

short to long-creeping, with wiry roots radiating from the 

underground-stem’s joints. 

Long-creeping stem of licorice fern. Vertical stem of northern wood fern.

Long-creeping stem

roots

Vertical stem

roots

Horsetails can have one kind of above-ground stem 

(monomorphic), or be dimorphic, with fertile and sterile 

above-ground stems. Spores are produced by cones that 

are situated at the tops of above-ground stems.

Fertile aboveground stem of 

common horsetail 

with a cone.

Above-ground 

stem of river 

horsetail.

Above-ground and underground stems of common horsetail.
8 9

Triangle moonwort fern

Botrychium lanceolatum

subsp. lanceolatum

This uncommon fern grows 

throughout south coastal Alaska on 

upper beach meadows, well drained 

meadows, subalpine and alpine 

meadows, and areas of historical 

human disturbance such as landing 

strips or roadsides. The deciduous 

leaf ranges in height from 1 to 

8 inches. The blade-like sterile 

segment is somewhat leathery, 

triangular and pinnate-pinnatifid 

to 2-pinnate-pinnatifid. The fertile 

segment is short-stalked and 

often divided into several stalked 

branches.

Common moonwort fern

Botrychium lunaria

An unusual-looking and relatively 

uncommon fern that grows 

across southern Alaska. It is often 

overlooked because it blends 

in so well with surrounding 

vegetation. This charismatic fern 

grows in habitats similar to those 

occupied by the triangle moonwort 

(described above). The deciduous 

leaf ranges in height from 1 to 

8 inches. The blade-like sterile 

segment is somewhat leathery, 

narrowly egg-shaped and pinnate 

with 2 to 6 pairs of fan-shaped 

pinna. The fertile segment is 

moderately long-stalked. The name 

moonwort comes from the pinna’s 

resemblance to a crescent moon. 

Several other moonworts are similar 

in appearance to this fern.

The moonworts, grapefern and rattlesnake fern are unusuallooking ferns. Their vertical underground stem produces a 

single leaf each year. This leaf is divided into a sterile segment 

and a fertile segment. The sterile segment is blade-like in 

Leathery grapefern

Botrychium multifidum

Occasional throughout southern 

Alaska this robust fern grows in 

muskegs, upper beach meadows, 

lake margins and subalpine 

meadows. The blade-like, sterile 

leaf segment is evergreen, leathery, 

broadly triangular, 3-pinnate and 

averages about 6 inches wide. This 

sterile leaf segment has a very 

short stalk, so it is often nestled 

down in the moss. The fertile 

segment is long-stalked and can 

grow up to 14 inches tall.

appearance. The fertile segment bears numerous spherical 

sporangia that collectively look like clusters of tiny grapes. 

The genus name, Botrychium, is derived from a Greek word 

referring to a bunch of grapes.

Rattlesnake fern

Botrychium virginianum

Occasional across southern Alaska. 

But, in some places this fern is 

abundant. It grows in upper beach 

meadows, forest edges and under 

open forest. This fern is locally 

abundant on Prince of Wales 

Island, along some roadways with a 

limestone substrate. The deciduous 

leaf ranges in height from 5 to 

20 inches. The blade-like sterile 

segment is thin-textured, broadly 

triangular and 2-pinnate-pinnatifid. 

It is placed about half way up the 

plant and appears to be lateral 

to the long-stalked fertile leaf 

segment.
10 11

Wood horsetail

Equisetum sylvaticum

A beautiful horsetail of the 

Chugach and northern Tongass 

Forest. Branches are branched 

again, giving this plant a 

very soft and lacy look. Our 

only horsetail with branched 

branches. It thrives best in areas 

with damp soil or in marshy 

situations. The deciduous stem 

grows to about 2 feet tall. 

Dimorphic, fertile stems are 

brownish; after 

spore release, 

becoming green 

and similar to 

sterile stems. 

Leaf tips are light 

brown, papery 

and connected in 

groups.

Common Horsetail

Equisetum arvense

This morphologically variable, 

deciduous horsetail is common 

throughout south coastal Alaska. 

It occupies a wide array of 

habitats, from wet to dry; and in 

disturbed areas can be weedy. 

Dimorphic; fertile stems are 

yellowish and branchless, and 

arise late in the spring, followed 

by the bright green, heavilybranched, sterile 

stems. 

River horsetail

Equisetum fluviatile

A very neat and organizedlooking horsetail, grows across 

southern Alaska. Usually found 

growing in shallow fresh water 

or marshy areas. The deciduous 

stem can grow to over 3 feet tall 

and they may or may not bear 

branches. The earliest stems to 

arise in the spring do not have 

branches. Numerous fused 

leaves (12-20 leaf tips). 

Leaf tips 

numerous

Fused 

leaves low on 

sterile stem

Stem joint

Variegated scouring rush

Equisetum variegatum subp.

alaskanum

Unbranched horsetails are 

called scouring rushes. This 

slender, unbranched plant 

grows across southern Alaska 

in many habitats, including 

gravel and sand bars, sandy 

lake shores, forest, moist 

meadows, alpine meadows; 

often in very wet situations. 

Stems are evergreen and quite 

variable in height and width, 

but can grow up to 20 

inches tall. Leaf tips 

are shiny black and 

somewhat incurved.

Stem with 

branches.

Branch

Leaf tips 

dark

Shiny, incurved 

leaf tips.
12 13

1/32 inch 

wide and 

one cell 

thick.

Sporophytes

Photo by Jiro Hayashi

Gametophytes

Blade 

about 1” 

long.

Wright’s filmy fern

Hymenophyllum wrightii

A minute evergreen fern, common as a gametophyte in the 

southern 3/4 of the Tongass. It is difficult to find because of its 

tiny size and mossy habitat. Gametophytes tangle with moss in 

the darkest areas on tree bases, the undersides of rotting logs 

and wet rock faces in wet lowland forests. The minute strap-like 

and branching “fronds” are less than 1/32 inch wide and one cell 

thick. They look like tiny thalloid liverworts. Sporophytes have 

not been found in Alaska but they are suspected to occur on the 

southern Tongass. These delicate 2-pinnate-pinnatified triangular 

fronds are about 2 inches long, petiole and blade each about 1 

inch long. The petiole and veins are dark brown. Sporangia are 

borne within bivalved structures on leaf lobe tips. The stem is 

long-creeping, thin and tangled, forming mats of fronds.

Western maidenhair fern

Adiantum aleuticum

A relatively common fern of south coastal Alaska, it is more 

common on the Tongass than the Chugach. It grows on moist 

rock faces, near streambanks and meadows from sea level to 

the alpine. Delicate, deciduous fronds range from 6 to 30 inches 

long with the fan-shaped, dichotomously-branched blade up 

to 18 inches long, often as broad as long. The blade is often at 

a right angle to the erect shiny dark brown petiole. The thin, 

papery pinnules are asymmetrical, with the lower side unlobed 

and upper side lobed. Sporangia are on the ends of the lobes, 

covered by the reflexed pinnule margin. The stem is short to 

long-creeping, resulting in scattered fronds. The distinctively 

shiny deep-brown petioles are sometimes used as decorative 

elements on Native baskets.

Bracken fern

Pteridium aquilinum var. pubescens

In Alaska this fern is known only from southeastern, where it is 

relatively common. It grows in meadows, open areas, muskegs 

and open forests. Deciduous, with very large fronds from 1 to 

3 feet tall. The leathery, triangular blade ranges from 8 inches 

to 2 feet long (and broad), 3-pinnate-pinnatified to 3-pinnate; 

atop a long tough petiole (8 inches to over 2 feet long). Sori are 

continuous along, and covered by, the inrolled leaf margin and 

an inconspicuous indusium. Fronds rise from a long-creeping 

horizontal stem. Considered to be a weedy fern, bracken often 

thrives in disturbed areas such as the roadside habitat shown 

here.
14 15

Fertile 

pinnules 

(rolled 

margins).

Sterile 

pinnules 

(toothed 

margins).

Green spleenwort Maidenhair spleenwort

Photo by Karen Dillman

Northern beech fern

Phegopteris connectilis

A relatively common fern across southern Alaska. Habitats 

include forests, forest edges, rock faces, subalpine meadows and 

areas near rivers. The deciduous fronds average 5 to 16 inches 

long. The narrowly triangular, pinnate-pinnatifid blade tapers 

gracefully toward the tip and is somewhat hairy. It is shorter 

than the very thin petiole and often held at right angles to the 

petiole. A distinguishing character of the northern beech fern is 

the reflexed lowest pinna pair, which point away from the tip of 

the blade. Fronds are widely scattered because they grow from 

long-creeping stems. 

American parsley fern

Cryptogramma acrostichoides

Generally infrequent across southern Alaska but can be 

abundant in some places. This small (4 to 9 inches tall) evergreen 

fern grows in rock crevices and talus slopes, especially in the 

mountains. The leaves are dimorphic. Sterile blades are narrowly 

triangular and leathery, 2 to 3 inches long, 2 to 3-pinnate, giving 

them a parsley-like look; pinnules have teeth or shallow lobes. 

The petioles are spreading, 2 to 4 inches long. Fertile blades with 

narrow pinnae; the inrolled margin of the pinnule covers the 

sporangia. These petioles are upright and longer (2 to 6 inches). 

Because of the short-creeping to erect stem, this fern often 

grows in bushy little clumps. 

Green spleenwort fern

Asplenium trichomanes-ramosum

Relatively rare on the Tongass and suspected to occur on the 

Chugach. This delightful fern grows in cracks in rocks, especially 

limestone. Its leaves are evergreen, small, up to 6 inches in 

length, less than 1/2 inch wide. The blade is long and narrow, 

pinnate, with numerous oval pinnules; the petiole is relatively 

short. The midrib and upper part of the petiole are green. Little 

clumps of fronds arise from short-creeping to vertical stems.

Maidenhair spleenwort fern

Asplenium trichomanes subsp. trichomanes

Extremely rare on the Tongass and not known on the Chugach. 

Similar to the green spleenwort, with the main difference being 

its shiny dark brown midrib and petiole.
16 17

Northwestern lady fern

Athyrium filix-femina

subsp. cyclosorum

One of the most common ferns in southern Alaska. Grows 

in forests, at forest edges and meadows from sea level 

to the subalpine. It can dominate the vegetation in some 

subalpine meadows. The deciduous fronds grow to 5 feet 

long. The blade is lance-shaped, widest at the middle, 

lacy, 2-pinnate-pinnatified; petiole is very short. Crowns 

of fronds arise from vertical to short-creeping stems. 

Similar to the mountain wood fern (above), but mountain 

wood fern is pinnate-pinnatified without further divisions, 

whereas lady fern’s pinnae are 2-pinnate-pinnatified.

Mountain wood fern

Thelypteris quelpaertensis

A common fern across southern Alaska. Grows at forest 

edges, open areas and meadows from sea level to the 

subalpine. On the Tongass it is abundant in the subalpine 

meadows; on the Chugach it is also abundant at forest 

edges at sea level. A handsome fern with deciduous 

fronds to 3 feet long. The blade is lance-shaped, widest at 

the middle, pinnate-pinnatifid; with a very short petiole. 

A dense crown of fronds rises from a vertical to shortcreeping stem. Similar in appearance to the northwestern 

lady fern (below), but the mountain wood fern’s pinnae 

are pinnate-pinnatified without further divisions. The lady 

fern’s pinnae are 2-pinnate-pinnatified.

Fragile fern

Cystopteris fragilis

This small deciduous fern is somewhat common across the 

region. It is most often found growing from cracks on rock 

faces from sea level to the alpine. The leaves are bright 

green, very soft and range in length from 2 to 12 inches. 

The leaf blade is narrow, pinnate-pinnatified to 2-pinnate, 

and somewhat longer than the petiole. The stem is shortcreeping, usually tucked well into the rocks. This results in 

loose sprays of the lax fronds emerging from the rocks. 
18 19

Photo by John Maunder.

Sterile pinnae

Fertile pinnae

Western oak fern

Gymnocarpium disjunctum

Very common across southern Alaska. It grows in open 

forests, forest edges and open areas from sea level to alpine. 

Fronds are deciduous and relatively small. The triangular 

blade averages 6 to 8 inches long (about as wide), 2 to 

3-pinnate-pinnatifid. The blade is held at a right angle to the 

petiole (photo looks straight down on the blade). The petiole 

is thin, straight and less than two times as long as the blade. 

Fronds arise from long-creeping stems. The common oak fern 

(Gymnocarpium dryopteris) also grows here; it is similar but 

less abundant. Its blade is generally smaller than the blade of 

western oak fern.

Rusty cliff fern

Woodsia ilvensis

Rare in southern Alaska, although several populations can be 

seen at Mendenhall Glacier near Juneau. This distinctive fern 

grows in open rocky areas or cracks in open rock faces in dryer 

areas from sea level to the alpine. The leaves are deciduous, 

to 7 inches long. The blade is narrowly lance-shaped, pinnatepinnatifid. The underside is fuzzy with rust colored scales and 

hairs. The petiole is 1/5 to 1/3 the length of the leaf. At the 

base of the leaf there is a distinctive joint where the leaf breaks 

off when it falls. Tufts of fuzzy fronds and old leaf bases arise 

from the vertical stem.

Deer fern

Blechnum spicant

Common across southern Alaska. Deer fern can be found 

in nearly all habitats but is most robust in open coniferous 

forests. Plants range in size from 8 inches to 2 feet tall. Leaves 

are pinnate and dimorphic. Sterile leaves are evergreen, shiny 

and somewhat spreading. The blade is long and narrow, 

widest at the middle; the petiole is relatively short. Fertile 

leaves are erect, deciduous, long and narrow. The petiole of 

fertile leaves is long, making them much taller than the sterile 

leaves. The rolled margins of the fertile pinnae give the fertile 

pinnae a skeletonized look. The stem is short-creeping to 

vertical, making a circular crown of fronds as shown here in 

a mature plant. Note the thin, erect fertile fronds rising from 

the center of the fern.
20 21

Note the short, dark-brown fertile frond arising from the center of the 

ostrich fern.

Ostrich fern

Matteuccia struthiopteris

In Alaska, known only from Southcentral, including the Chugach. 

An uncommon dimorphic fern; it grows in open forests and in 

areas associated with streams. Sterile leaves are bright green, 

large and up to 4 feet in length. The blade is bright green, 

broadly lance-shaped, widest above the middle and pinnatepinnatifid. The petiole is very short. Fertile leaves are shorter 

than the sterile leaves. They are erect, brown and club-like in 

appearance because the fertile pinnae are pressed together 

toward the frond tip. Ostrich fern is used as a landscaping plant 

in Southcentral Alaska. 

Northern wood fern

Dryopteris expansa 

A very common fern across southern 

Alaska. Abundant in open forests and 

forest edges from sea level to the 

subalpine. The fronds are late-deciduous 

and can reach a length of 3 feet. The 

narrowly triangular, 2-pinnate-pinnatified 

to 3-pinnate blade is a little longer than 

the petiole. Open crowns of fronds arise 

from vertical stems. In the past, Northwest Coast natives cooked 

and ate these stems as a survival food. The cutting and texture 

of the leaf blade is similar to the northwestern lady fern (p. 17) 

but the triangular blade shape makes it easy to distinguish the 

northern wood fern from the broadly lance-shaped leaves of the 

northwestern lady fern. 

Fragrant wood fern 

Dryopteris fragrans

This evergreen fern grows in the western part of the Chugach 

Forest, especially on the Kenai Peninsula and in the Chugach 

Mountains. Habitats include rocky bluffs, talus and scree slopes 

from sea level to the alpine. The leaves are deep green, somewhat 

leathery and very scaly on the lower surface. They range in length 

from 3 to 12 inches, with an average of about 7 inches. The leaf 

blade is narrow, pinnate-pinnatified to 2-pinnate and about three 

times as long as the petiole. The withered and curled remains of 

fronds from previous years remain attached to the stem at the 

base of the fern. These withered fronds are visible at the bottom 

of the photo. The stem is short-creeping, resulting in dense tufts 

of fronds among the rocks.

Photo by Rob DeVilice
22 23

Bulblet located 

near tip of leaf. Photo by Karen Dillman

Anderson’s sword fern

Polystichum andersonii

Rare on the Chugach, known only on the 

east side of that Forest. Generally uncommon on the Tongass 

but common in the appropriate habitat. Found in well drained 

areas associated with rivers, often among rocks in well drained 

slopes under alder. Shiny evergreen fronds grow to 3 feet in 

length. The blade is lance-shaped, widest at the middle, pinnatepinnatifid. The petiole is about 1/6 of the leaf in length. This 

fern is distinguished from the other Polystichum by the bulblet 

produced toward the tip of the frond. When pressed to the 

ground the bulblets grow into new plants; therefore this fern 

often grows in colonies 

(note small ferns in the 

upper left photo). The 

crown of fronds arises 

from a vertical stem.

Bulblet developing into a 

new fern. Note the tiny fern 

frond above the bulblet.

Braun’s holly fern

Polystichum braunii 

This fern is generally 

uncommon across southern 

Alaska but it is more common on the Tongass than on the 

Chugach. It grows in well drained areas associated with rivers, 

often among rocks in well drained slopes under alder. The 

somewhat shiny evergreen fronds grow to 3 feet long. The blade 

is lance-shaped, widest at the middle and 2-pinnate (pinnatepinnatifid toward leaf tip). The petiole is about 1/6 of the leaf in 

length. The vase-like crown of fronds arises from a vertical stem. 

Distinguished from Anderson’s sword fern (see above) by its 

2-pinnate pinnae and lack of bulblet; distinguished from Alaska 

sword fern (p. 25) by its 2-pinnate blade, and duller foliage. 

Holly fern

Polystichum lonchitis

Generally uncommon across the southern Alaska but more 

common on the Tongass than the Chugach. It grows from cracks 

in rocks, among boulders and on cliff faces from sea level to 

alpine. Holly fern is often associated with limestone. The fronds 

are glossy, stiff and evergreen, to 18 inches long. Deep green 

blades are narrowly lance-shaped, widest at the middle or just 

above the middle and pinnate. The petiole is extremely short; 

essentially the entire frond is blade. Fronds are often erect, 

arising from a vertical stem. It is distinguished from the common 

sword fern (p. 25) by its shorter, narrower fronds, smaller stature 

and an extremely short petiole.
24 25

Growing on red alder

Licorice fern

Polypodium glycyrrhiza

Common on the Tongass, but not as common on the Chugach. 

Often grows among moss on rocks or on trees (sometimes high 

in the trees), frequently near the beach. Grows from sea level 

to subalpine. Fronds are evergreen and vary considerably in 

size from 2 to 22 inches long, averaging about 8 inches long. 

The pinnate blade is narrowly egg-shaped. Pinna shape can be 

variable with rounded or pointed tips and various degrees of 

toothing along the margins. The petiole is relatively long, about 

1/3 the length of the leaf. Leaves are often widely spaced, arising 

from a thick long-creeping stem. The stem tastes like licorice, 

thus the name, licorice fern.

Common sword fern

Polystichum munitum

The iconic fern of the northwest

coast. Common on the Tongass from Frederick Sound south. 

It grows at forest edges, scree at the bases of cliffs and well 

drained forests. Fronds are deep green, arching, evergreen, to 

4 feet long. The blades are narrowly triangular and pinnate. 

The lowest pinnae are long and nearly the same size as the 

adjacent pinnae. The petiole is about 1/4 the length of the leaf. 

Fronds arise from a vertical stem. Since fronds can stay green 

for several years these ferns can be impressive in the number 

of new and old fronds they bear. Somewhat similar to the holly 

fern (p. 23), but the western sword fern is distinguished from it 

by its large fronds, long basal pinnae and longer petiole.

Alaska sword fern

Polystichum setigerum

This fern is uncommon on the Tongass

and not known to occur in the Chugach. It can be common in 

appropriate habitat. It grows in well drained areas associated 

with rivers, often among rocks in well drained slopes under 

alder. The attractive, glossy evergreen fronds to 2 feet long. 

The blade is lance-shaped, widest at the middle with pinnae 

pinnate-pinnatifid to 2-pinnate. The petiole is relatively short, 

about 1/8 to 1/6 the length of the leaf. The crown of fronds 

arises from a vertical stem. Distinguished from Anderson’s 

sword fern (p. 23) by the lack of a bulblet; distinguished 

from Braun’s holly fern (p. 23) by glossy foliage and pinnatepinnatifid pinnae.

Growing on rocks
26 27

Checklist of the Ferns 

of the Alaska Region

Scientific and common names are shown. Names are listed 

alphabetically by scientific name within the fern families. 

Families are arranged according to Smith et al., (Taxon 55: 

705-731. 2006). Ferns discussed in detail and pictured in this 

brochure are marked with an asterisk.

OPHIOGLOSSACEAE

Adder’s Tongue Family

Botrychium alaskense, Alaskan grapefern

Botrychium ascendens, Ascending moonwort fern

Botrychium lanceolatum subsp. lanceolatum, 

 Triangle moonwort fern*

Botrychium lunaria, Common moonwort fern*

Botrychium minganense, Mingan moonwort fern

Botrychium montanum, Mountain moonwort fern

Botrychium multifidum, Leathery grapefern*

Botrychium pinnatum, Northwestern moonwort fern

Botrychium simplex, Least moonwart fern

Botrychium spathulatum, Spatulate moonwort fern

Botrychium tunux, Moosewort fern

Botrychium virginianum, Rattlesnake fern*

Botrychium yaaxudakeit, no common name

EQUISETACEAE

Horsetail & Scouring Rush Family

Equisetum arvense, Common horsetail*

Equisetum fluviatile, River horsetail*

Equisetum hyemale subsp. affine, Common scouring rush

Equisetum palustre, Marsh horsetail

Equisetum pratense, Meadow horsetail

Equisetum scirpoides, Dwarf scouring rush

Equisetum sylvaticum, Wood horsetail*

Equisetum telmateia, subsp. braunii, Giant horsetail

Equisetum variegatum subsp. alaskanum, 

 Alaskan variegated scouring rush*

Equisetum variegatum subsp. variegatum, 

 Variegated scouring rush

HYMENOPHYLLACEAE

Filmy Fern Family

Hymenophyllum wrightii, Wright’s filmy fern*

DENNSTAEDTIACEAE

Bracken Fern Family

Pteridium aquilinum var. pubescens, Bracken fern*

PTERIDACEAE

Maidenhair family

Adiantum aleuticum, Western maidenhair fern*

Cryptogramma acrostichoides, American parsley fern*

Cryptogramma sitchensis, Alaska parsley fern

Cryptogramma stelleri, Steller’s rock-brake fern

ASPLENIACEAE

Spleenwort Fern Family

Asplenium trichomanes-ramosum, Green spleenwort fern*

Asplenium trichomanes subsp. trichomanes, 

 Maidenhair spleenwort fern*

THELYPTERIDACEAE

Female Fern Family

Phegopteris connectilis, Northern beech fern*

Thelypteris quelpaertensis, Mountain wood fern* 

WOODSIACEAE

Cliff Fern Family

Athyrium americanum, American alpine lady fern

Athyrium filix-femina subsp. cyclosorum,

 Northwestern lady fern*

Cystopteris fragilis, Fragile fern*

Cystopteris montana, Mountain bladder fern

Gymnocarpium disjunctum, Western oak fern*

Gymnocarpium dryopteris, Common oak fern

Woodsia alpina, Alpine cliff fern

Woodsia glabella, Smooth cliff fern

Woodsia ilvensis, Rusty cliff fern*

Woodsia scopulina subsp. scopulina, Mountain cliff fern

BLECHNACEAE

Chain Fern Family

Blechnum spicant, Deer fern*

ONOCLEACEAE

Sensitive Fern Family

Matteuccia struthiopteris, Ostrich fern*

DRYOPTERIDACEAE

Wood Fern Family

Dryopteris expansa, Northern wood fern*

Dryopteris fragrans, Fragrant wood fern*

Polystichum andersonii, Anderson’s sword fern*

Polystichum braunii, Braun’s holly fern*

Polystichum kruckebergii, Kruckeberg’s holly fern

Polystichum lonchitis, Holly fern*

Polystichum munitum, Common sword fern*

Polystichum setigerum, Alaska sword fern*

POLYPODIACEAE

Polypody Fern Family

Polypodium glycyrrhiza, Licorice fern*
The Alaska Region of the Forest Service includes the Tongass 

National Forest, the nation’s largest at 17 million acres, and 

Chugach National Forest, the nation’s second largest at 5 million 

acres. The Tongass encompasses most of southeastern Alaska 

(Alaska panhandle) and the Chugach roughly surrounds Prince 

William Sound. 

This brochure was prepared by the Forest Service, Alaska Region 

Botany program. Text, diagrams and photographs by Mary 

Stensvold unless otherwise noted. For more information about 

ferns and other wild plants of the Alaska Region go to:

http://www.fs.fed.us/wildflowers/regions/alaska/index.shtml

Suggested reading

A Field Manual of the Ferns & Fern Allies of the United

 States & Canada, David Lellinger 

A Natural History of Ferns, Robbin Moran 

Encyclopedia of Garden Ferns, Sue Olson

Ferns and Fern Allies of Canada, 

 William Cody & Don Britton 

Fern Growers Manual, 

 Robbin Moran and Barbara Hoshizaki

Ferns and Gymnosperms, 

 Flora of North America, North of Mexico, Volume 2,

 Alan Smith and Herb Wagner, Jr., eds; 

How to Know the Ferns and Fern Allies, John Mickel. 

The USDA is an equal opportunity provider and employer.

Cover photograph: Aleutian maidenhair fern, western sword 

fern, western oak fern and maidenhair spleenwort. These ferns 

are growing on a limestone outcrop near the mouth of a cave 

in a coniferous forest on Prince of Wales Island on the Tongass 

National Forest. Photo by Brad Krieckhaus.