Hardy Fern Home

D. intermedia resources
Descriptive
Connecticut Botanical SocietyConnecticut Botanical Society
diagnostic pointersdiagnostic pointers
Ferns of the NorthwoodsFerns of the Northwoods
Distribution
North AmericaNorth America
WorldWorld
Drawing
Britton & BrownBritton & Brown
Flora
Flora of North AmericaFlora of North America
Monograph
Hoshizaki and WilsonHoshizaki and Wilson
Photo
fertile pinnafertile pinna
herbarium specimen, then photos of top and bottom of a frondherbarium specimen, then photos of top and bottom of a frond
Photo index
PlantSystematics.org, diagnostic photosPlantSystematics.org, diagnostic photos
inoperativeseveral photos, but particularly the glandular hairs (link inoperative)

All Ferns
  Dryopteridaceae
   Dryopteris
     aemula  affinis
     amurensis  arguta
     bissetiana  campyloptera
     carthusiana  caucasica
     celsa  championii
     clintoniana  crassirhizoma
     cristata  cycadina
     cystolepidota  decipiens
     dilatata  erythrosora
     expansa  filix-mas
     formosana  fragrans
     fuscipes  goldiana
     hondoensis  intermedia
     kuratae  lacera
     lepidopoda  ludoviciana
     marginalis  mindshelkensis
     oreades  pacifica
     polylepis  pseudo-filix-mas
     purpurella  remota
     sacrosancta  saxifraga
     sieboldii  stewartii
     sublacera  tokyoensis
     uniformis  varia
     wallichiana

 Other Genera
    Adiantum  Arachniodes
    Aspidotis  Asplenium
    Astrolepis  Athyrium
    Blechnum  Cheilanthes
    Cryptogramma  Cyrtomium
    Cystopteris  Dennstaedtia
    Deparia  Diplazium
    Gymnocarpium  Lygodium
    Matteuccia  Onoclea
    Oreopteris  Osmunda
    Pellaea  Phegopteris
    Pleopeltis  Polypodium
    Polystichum  Pteridium
    Pteris  Pyrrosia
    Thelypteris  Woodsia
    Woodwardia
 
Dryopteris intermedia (Muhlenberg ex Willdenow) A. Gray

Fancy fern, Evergreen wood fern

Etymology Intermedia, presumably intermediate between D. carthusiana and D. campyloptera.
Description Rhizome: erect, stout.
Frond: 70 cm high by 20 cm wide, evergreen, monomorphic, blade/stipe ratio: 2:1 to 3:1.
Stipe: grooved, green, scattered, tan scales, more towards the base, vascular bundles: 5 in an arc.
Blade: 3-pinnate at the base, gradually less above, ovate, herbaceous, glandular.
Pinnae: 12 to 14 pair, anadromous on the lowest pinna pair, opposite pinnules above, lanceolate-oblong and more-or-less in plane of blade; lowest pair lanceolate, and not reduced in size; pinnules inner, lower pinnule on the lowest pinna somewhat shorter than the next one; costae grooved above, continuous from rachis to costae; margins serrate, spiny; veins free, forked.
Sori: round, in 1 row between midrib and margin, indusium: reniform, at a sinus, sporangia: brown, maturity: midsummer.
Culture Habitat: moist, rich woods, especially in limestone areas. Distribution: northeastern North America. Hardy to -35C, USDA Zone 3.
Distinctive Characteristics Distinguished from the other spinulose wood ferns by the first lower pinnules of the lowest pinnae the same length or shorter than the second pinnule.
Synonyms
Aspidium intermedium Muhlenberg ex Willdenow
Dryopteris austriaca (Jacquin) Woynar var. intermedia (Muhlenberg ex Willdenow) C. V. Morton
Dryopteris spinulosa (O. F. Mueller) Watt var. intermedia (Muhlenberg ex Willdenow) L. Underwood
Dryopteris intermedia
Dryopteris intermedia.  Illustration by Edgar Paulton, from How to Know the Ferns and Fern Allies, John T. Mickel, 1979 Wm. C. Brown Co.
Notes
Variability A diagnostic character for D. intermedia among the spinulose wood ferns is the shorter first downward-pointing pinnule on the lowest pinna. However, there is great variability, and an anomalous example is easy to find -- see the photo below. On average the character holds.
Dryopteris intermedia
Dryopteris intermedia. Lowest pinna: anadromic, first downward-pointing pinnule longer than the next. This is anonomalous; see the notes.  Scan: Tom Stuart
Dryopteris intermedia glands
Dryopteris intermedia. Glandular hairs just below upper sorus are diagnostic. A hand lens required. There are better examples in the resources.  Scan: Tom Stuart
Dryopteris intermedia vascular bundles
Dryopteris intermedia. Vascular bundles at stipe base: five, the two largest visible to the naked eye, the others only through a hand lens. In some cases the smallest bundles disappear before the top of the stipe, leaving only three.  Scan: Tom Stuart
Dryopteris intermedia
Dryopteris intermedia. a) frond; b) fertile pinnule, spiny.  Illustration by V. Fulford from Ferns and Fern Allies of Canada, William J. Cody and Donald M. Britton, 1989, Agriculture Canada, used with permission.
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