Category Archives: Ferns

Shield fern (dryopteris expansa)

Shield fern (dryopteris expansa, also known as the spiny wood fern), is a deciduous fern that prefers most forests in the Pacific Northwest. The fronds are erect, clustered but spreading, and can reach up to one meter tall. It has asymmetrical pinnae at the pair closest to the base, and female ferns are three times pinnate while males are two times. The frond is shaped like a triangle, with and oblong shape in the middle and a fast taper at the end. It can have five to twenty pairs of leaflets, each with their own pairs of about 10 leaflets. Sori are rounded and partially covered.

  • Deciduous, erect and clustered, can reach one meter tall
  • Females are three-times pinnate, while males are two times
  • Asymmetrical pinnae at pair closest to base
  • Frond shaped like a triangle, with five to twenty pairs of leaflets



Pacific sword fern (polystichum munitum)

The Pacific sword fern (Polystichum munitum) is a large, evergreen fern that grows in moist locations, and is very abundant and widespread in the coastal Pacific Northwest. It is a once-pinnate (leaves are basal) plant that can grow up to 1.5 meters tall.

The leaves are lancolate and erect, and usually grouped together at the base, forming spiral patterns of growth. The pinnae are attached at one point, and are sharply toothed, alternating as they go up on the stalk. Each pinna is about 1-15 cm long, with sori underneath that occupy two rows, producing spores that are bright yellow.

  • Fronds can get up to 1.5 meters tall, once-pinnate
  • Fronds are lancolate shaped and resemble swords
  • Pinna have serrated margins and are attached at one point on the axis
  • Sori underneath pinna are double-rowed

Maidenhair fern (adiantum pedatum)

Also known as Adiantum aleuticum, the maidenhair fern (Adiantum pedatum) is an unusual fern that resembles plants more than ferns. The branches are palmately arranged and are where the leaves become fronds. Stipes can be dark purple or brown, 15 to 60 centimeters tall. The top of the stalk of the plant divides twice to create the fronds. The leaflets are fan or oblong shaped and are in a linear, consistent fashion with a little bit of tapering at the end of the frond, and are usually at right-angles to the stalk. Sori are oblong and on edges of leaflets.



  • Branches are palmately arranged, where leaves become
  • Stipes dark purple or brown, 15-60 cm tall
  • Top of stalk divides twice to produce fronds
  • Leaflets are fan or oblong shaped
  • Arranged linearly with slight tapering at end of frond





Lady fern (athyrium filix-femina)

The Lady Fern (Athyrium filix-femina) is a deciduous fern that thrives in wet, riparian and swamp conditions at any elevation. They are twice pinnate and fronds can grow to two meters tall, erect and clustered. The fronds are lancolate and taper at both ends, and pinnae are in 20-40 pairs that have a single attachment to the axis. Fronds resemble sword ferns but are more ‘football’-shaped, tapering at both ends

Not to be confused with the shield fern, the lady fern tapers toward the base at both ends, while the shield fern is more triangular-shaped. Sori are curved and elongated.

  • Fronds can get to 2 meters tall and are twice pinnate, clustered and erect
  • Fronds are lancolate and taper at both ends
  • 20-40 pairs of pinnae attached at one point on the axis
  • Thrives in wet, riparian and swampy conditions

Goldenback fern (pityrogramma triangularis)

The goldenback fern (pityrogramma triangularis, or Pentagramma triangularis) is a smaller evergreen fern located in the southern end of the Pacific Northwest. It is three times pinnate and can get to 35 centimeters tall, and its pinnae are completely attached to the axis. Its stems are black and it gets its name from the golden-white powder underneath the leaves, and share the space with the sori, which follow the veins on the underside of the leaf. They prefer partly shaded, dry, rocky rough biospheres, in lower to middle elevations. Like the shield fern, the pair of leaflets closest to the base contains asymmetrical pinnae.



  • Smaller, evergreen fern, three times pinnate, can reach 35 cm
  • Stems are black, underside of leaf is golden
  • Prefer partly shaded, rocky and dry areas
  • Asymmetrical pinnae at the base of frond
  • Pinnae attach completely to the axis

Goldenback fern

Deer fern (blechnum spicant)

The deer fern (Blechnum spicant) is an evergreen fern similar to the sword fern (polystichum munitum). It lives in moist and wet forests, and other areas served with lots of water. Like the sword fern, they are basal leaves/once pinnate, but differ from the sword fern in that the pinnae are entirely attached to the leaf, whereas sword ferns have stems attaching to the axis. The deer fern is unique in that it has two different kinds of ferns. One kind has shorter, wider leaves that look similar to a weed trimmer, with alternating pinnae attaching to the axis. The other kind resembles the sword fern, with a lancolate shape that bulges in the middle. Both have continuous sori on the underside of the leaf near the margin.

  • Two different kinds of fronds: one has shorter, wider leaves, and the other has longer, lancolate leaves; both types attach fully at the base
  • Basal/once pinnate leaves reaching from the bottom and stand erect
  • Continuous sori underneath leaf


Bracken fern (pteridium aquilinum)

The bracken fern (Pteridium aquilinum) is a deciduous fern native to many different environments including roadsides, burns, meadows, dry and set forests, and other areas that it can get sun (it loves sun). It can reach between three and five meters tall, and has erect, solitary ferns that are three times pinnate. The pinnae of the frond are triangular shaped and hairy with ten or more pairs per leaflet, with rolled under margins.  The lower pair of leaflets are very triangular, and get more and more reduced as it reaches the end of the frond. Sori are continuous and marginal, protected by the rolled leaf margin.


  • Deciduous fern that likes many different environments
  • Can get between 3 and 5 meters tall
  • Erect, solitary ferns that are three times pinnate
  • Pinnae are triangular shaped and hairy, with 10+ pairs per leaflet
  • Rolled margins