Ferns-misc12017-08-14T14:22:29+00:00

Ferns — Various Families

Ferns are not flowering plants and lack the separate male and female parts that form the basis of most flowering plants’ reproductive processes. Instead, ferns have spores which, when they fall in a suitably moist, shady place, are able to trigger the fern’s reproductive cycle. Partly because of these differences, discussions of ferns use some different terminology:

  • A fern’s leaf is called a frond divided into pinnae which are in turn subdivided into pinnules
  • The underside of the pinnules contain sori which in turn contain the sporangia which their turn contain the spores
  • Sori may be covered by a membrane-like indusium.  A false indusium is  a covering formed by a reflexed margin of the pinna / pinnule.  Not all ferns have clearly defined sori

All ferns included here are native to California.

Chain Fern – Woodwardia fimbriata (Blechnaceae: Deer Fern family)

Frond:

1–2 m

Pinnate:

2 ×

Pinnule:

Serrated

Sori:

Oblong

Indusium:

Yes

Notes:

This is one of the largest ferns, favouring damp conditions and generally found near streams or seeps. The pinnae are clearly separated and pinnules are each pointed and very finely serrated. The common name derives from the neat lines created by the oblong sori and which are visible on both the upper andlower surfaces of each pinnule. As the sporangia mature, the indusium opens lengthways like a lid so as to reveal the sporangia underneath.

Western Bracken Fern – Pteridium aquilinum var. pubescens (Dennstaedtiaceae: Bracken family)

Frond:

< 1.5 m

Pinnate:

3 ×

Pinnule:

Entire

Sori:

Near margin

Indusium:

False

Notes:

The fronds are at first sight similar to those of Wood Fern (Dryopteris arguta) but Bracken Fern has a distinct stem (typically about 1 m tall) with fronds branching off it whereas the fronds of Wood Fern all arise directly from the fern’s base. Also unlike Wood Fern,, it is deciduous.  Sori are concentrated around the margins of the pinnules, more or less covered by the false indusium. This fern tends to prefer open areas where it can spread extensively.

Wood Fern – Dryopteris arguta (Dryopteridaceae: Wood Fern family)

Frond:

30–60 cm

Pinnate:

(1)2 ×

Pinnule:

Finely toothed

Sori:

Round

Indusium:

Yes

Notes:

This is certainly the commonest evergreen fern to be found in oak woodlands, each plant producing several fronds from its base (so differentiating it from Western Bracken Fern (Pteridium aquilinum) which has a distinct stem with fronds branching  from it). The fronds are lanceolate but the pinnules tend to be rounded with all of the veins ending in spine-tipped teeth. The sori are covered by a roundish or kidney-shaped indusium. The fronds feel a little tougher and firmer and are less broadly triangular than those of Lady Fern (Athyrium filix-femina) with which it could be confused.

Sword Fern – Polystichum munitum (Dryopteridaceae: Wood Fern family)

Frond:

60–140 cm

Pinnate:

1 ×

Pinnule:

Serrated

Sori:

Round

Indusium:

Yes, ciliate

Notes:

This is one of the most commonly found ferns, in oak woodland and, especially, in redwood forests. Each plant may produce many shiny, deep green fronds with slender pinnae which have serrated margins. The broadened base of the pinnae is said to resemble a sword’s hilt. The axis of the frond (the “rachis”) has brown scales.  The sori are round. Like other Polystichum, indusia, if present, have marginal hairs and are “peltate”, i.e. with a stem attached to the lower surface like a parasol.

California Sword Fern – Polystichum californicum (Dryopteridaceae: Wood Fern family)

Frond:

40–100 cm

Pinnate:

1–2 ×

Pinnule:

Various

Sori:

Round

Indusium:

Yes, ciliate

Notes:

This is similar to Dudley’s Sword Fern (Polystichum dudleyi) but with some subtle differences. The base of the pinnules is clearly tapered and without lobes. Multiple sori on each pinnule appear to be common. Indusia, if present, are, as with Dudley’s Sword Fern, delicate and with hairy margins. The fronds are much softer than Sword Fern (Polystichum munitum). The species is thought to be a sterile hybrid between P. munitum and P. dudleyi.

Dudley’s Sword Fern – Polystichum dudleyi (Dryopteridaceae: Wood Fern family)

Frond:

50–100 cm

Pinnate:

2 ×

Pinnule:

Various

Sori:

Round

Indusium:

Yes, ciliate

Notes:

This produces several arching fronds, soft to the touch, unlike Sword Fern (Polystichum munitum). Pinnules are abruptly tapered at their base, often lobed and ore or less divided or serrate to pinnately cut. Indusia, if present, are delicate and with hairy margins. Found in redwood and mixed evergreen forests.

Western Lady Fern – Athyrium filix-femina var. cyclosorum (Woodsiaceae: Cliff Fern family)

Frond:

25–130 cm

Pinnate:

1–2 ×

Pinnule:

Lobed /  toothed

Sori:

Round to J-shaped

Indusium:

Round to J-shaped

Notes:

This is easily mistaken for Wood Fern (Dryopteris arguta) but its fronds are significantly larger and more broadly triangular, noticeably softer to the touch and generally  paler in color. The lower 2–4 pinnae are much shorter than those immediately above. Sori may be round, oblong or J-shaped. Indusia, if present, will be similarly shaped, attached on the inner side of the sori, often with hairy margins. Found in meadows and streambanks.