Woodsia species

Cliff Ferns

Rusty Woodsia
Jap Lake, BWCAW
Photo © 2001 by Earl J.S. Rook

Flora, fauna, earth, and sky...
The natural history of the northwoods

Name:

• Woodsia, for English botanist Joseph Woods (1776-1864).
• Common name from the preferred habitat of these species.
• Other common names include Woodsia, Hällebräknar (Swe), Kiviyrtit (Fin), Wimperfarn (Ger)

Taxonomy:

• Kingdom Plantae, the Plants
  • Division Polypodiophyta, the True Ferns
    • Class Filicopsida
      • Order Polypodiales
        • Family Dryopteridaceae, the Wood Ferns
          • Genus Woodsia, the Cliff Ferns
• Taxonomic Serial Number: 17736
• North Country Woodsia species
  • alpina, Alpine Woodsia (Species of Special Concern-MN)
  • glabella, Smooth Woodsia (Threatened Species-MN)
  • ilvensis, Rusty Woodsia
  • oregana, Oregon Woodsia
  • scopulina, Rocky Mountain Woodsia (Threatened Species-MN)
• About 30 species worldwide, mostly north temperate regions and higher elevations in the tropics.
• Genus Cystopteris probably the closest relative.
• North American Woodsia fall into two natural groups that might be recognized as subgenera.
  • Circumboreal Woodsia, (Woodsia ilvensis , Woodsia glabella , and Woodsia alpina), show clear affinities to Eurasian species and are marked by
    • articulate petioles
    • smooth or crinkled edge leaflets (pinnules)
    • uniformly colored stem scales
    • indusial segments uniseriate throughout
    • chromosome base numbers of 39-41
  • Endemic Woodsia, (Woodsia oregana and Woodsia scopulina) are found only in our hemishpere, and are marked by
    • petioles that are not articulate
    • toothed edge leaflets (pinnules)
    • often bicolored stem scales
    • indusial segments multiseriate at the base
    • chromosome base number of 38
  • Hybridization is common within these two groups, but intergroup hybrids are relatively rare.

Description:

• A group of small ferns of rocky places.
• Fronds monomorphic, either deciduous or evergreen, erect to ascending from the ground-level stems, unbranched, but rarely horizontal; arising close together amid a cluster of persistent petiole bases; usually less than 6" high.
  • Petiole 1/5-3/4 length of blade, base not conspicuously swollen; smooth or more often hairy; hairs more than the diameter of petiole.
  • Blades 1¼"-6" (rarely to 10") long, linear or lanceolate when mature, with inconspicuous veins; most species hairy.
• Rookstalks compact to creeping, ascending or erect (rarely horizontal), stolons absent.
  • Roots black
• Sori round, with distinct indusium; often sufficiently numerous to cover the underside of the frond [photo].
  • Indusium of narrow, hair-like segments encircling sorus, one row of cells many times longer than wide, and longer than the sporangia; persistent but often obscure in mature sori.
  • Spores brownish

Identification:

• Identifiable as Woodsia by
  • articulate bases to the petioles and the accumulation of petiole bases that have broken off below the articulation.
  • relatively small size for our area
  • affinity for rocky habitats
• Distinguished from other small ferns of rocky places by
  • twice-cut fronds
• Field Marks
  • hairs and scales on fronds and leafstalks
  • presence or absence of stem segmentation or articulation
  • color of mature leaf stalk
• Woodsia Identification for Amateurs
  1. Look for the scattered hairs and scales characteristic of this genus. If you don't find any, look for dark-colored leaf stalks. If all you can find are smooth greenish stalks with smooth blades, then you have Woodsia glabella or Smooth Woodsia. This will be a very small fern, with fronds less than ½" wide and fan-shaped lower leaflets. This fern is classified as Threatened in Minnesota and has been found in Cook and Lake Counties, but not St. Louis.
  2. If you have a more typical Woodsia, check the leaf stalk to see if it is segmented, with a node clearly visible well above the base. In our area, we have two Woodsia with a segmented or articulated leaf stalk, the robust Woodsia ilvensis or Rusty Woodsia, and the more delicate Woodsia alpina, or Mountain Woodsia.
  • Rusty Woodsia is our most common Woodsia and has abundant hairs and scales. Its largest leaflets (pinnae) have 4-9 pairs of secondary leaflets (pinnules).
  • Alpine Woodsia is much less common, classified as a "Species of Special Concern" in Minnesota and found in Cook and Lake Counties, but not St. Louis. It has only scattered hairs and scales, and its largest pinnae have but 1-3 pairs of pinnules.
  3. If, on the other hand, your more typical Woodsia has an unsegmented leaf stalk, it is one of our two remaining species, Woodsia scopulina (Rocky Mountain Woodsia) or Woodsia oregana (Oregon Woodsia).
  • Rocky Mountain Woodsia is classified as a Threatened species in Minnesota and in our area is known only from Cook County in the far northeastern corner of the state. It is best identified by its hairs which are concentrated along the midrib on both surfaces, and by its mature leafstalks, which are typically a reddish brown to dark purple in color and relatively brittle, shattering easily.
  • Despite its western name, Oregon Woodsia occurs throughout our area. Unlike its less common cousin (with another western name), it lacks a concentration of hairs along the midrib. Its mature leafstalks are often light brown to straw-colored and though occasionally reddish brown to dark purple they remain much more pliable than the leafstalks of the Rocky Mountain Woodsia, and resistant to shattering.
  4. In the event, frustrating though it may be, that your specimen seems to fall somewhere between these species characteristics, you may have stumbled across a Woodsia hybrid. This genus of fern is notorious for hybridization and hybrids of Rocky Mountain Woodsia and Oregon Woodsia (Woodsia x maxonii), Oregon Woodsia and Rusty Woodsia (Woodsia x abbeae), and Rusty Woodsia and Alpine Woodisa (Woodsia x gracilis) have all been found in northeastern Minnesota. Identification of the hybrids is beyond the scope of this effort, other than to note that the hybrids typically have characteristics midway between those of the two parent species.

Distribution:

• Circumpolar. Arctic, or low arctic, or alpine.

Habitat:

• Usually growing on rock

Fire:

Associates:

History:

Uses:

Reproduction:

• By spore and vegetatively by rhizome

Propagation:

• By rhizome division

Cultivation:

• Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
• Rarely available commercially.

Links:

• Den Virtuella Floran, Naturhistoriska riksmuseet, Stockholm

Comments: