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Dryopteris intermedia — evergreen wood fern

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Facts

Evergreen wood fern is a species with leaves that remain green through the winter (i.e., they do not senesce in the fall as do closely related species). The leaves are thought to contribute to early spring growth by photosynthesizing before the new leaves have fully emerged.

Habitat

Alpine or subalpine zones, forests, wetland margins (edges of wetlands)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
  • terrestrial
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf divisions
  • the leaf blade is three times compound (divided into leaflets, which are further divided into leaflets, which are further divided into leaflets), or more
  • the leaf blade is twice compound (divided into leaflets, which are further divided into leaflets)
Plant growth form
the leaves grow from a rhizome growing at or below the ground
Spore-bearing leaflets
the spore-bearing fronds are similar in size and shape to the sterile fronds
Sorus shape
the sori are circular or kidney-shaped
Leaf stalk scales
the leaf stalk has scales
Leaf stalk hairs
the leaf stalk has hairs
Leaf blade length
25–50 cm
Leaf vein tips
the veins end in small round expanded areas, and do not reach the edge of the leaf blade
Show all characteristics

  • Growth form

    Life form
    the plant is herbaceous and terrestrial
    Life stage
    the plant is visible as a typical leaf-bearing fern (sporophyte)
    Spore-bearing leaflets
    the spore-bearing fronds are similar in size and shape to the sterile fronds

  • Leaves

    Features of leaves
    there are no special features on the leaves
    Leaf blade length
    25–50 cm
    Leaf blade shape
    the leaf blades are widest above the base, then taper broadly towards the tip (ovate)
    Leaf blade width
    At least 13 cm
    Leaf divisions
    • the leaf blade is three times compound (divided into leaflets, which are further divided into leaflets, which are further divided into leaflets), or more
    • the leaf blade is twice compound (divided into leaflets, which are further divided into leaflets)
    Leaf lifespan
    the leaves remain green all year round, or are green in winter
    Leaf stalk color
    yellow to brown
    Leaf stalk hairs
    the leaf stalk has hairs
    Leaf stalk length
    100–300 mm
    Leaf stalk relative length
    the leaf stalk is more than a quarter, but less than three quarters as long as the blade
    Leaf stalk scale location
    • the scales are present on both the lower and upper halves of the leaf stalk
    • the scales are present only on the lower half of the leaf stalk
    Leaf stalk scales
    the leaf stalk has scales
    Leaf stalk vessels
    3 to 9 bundles
    Leaf vein branching
    the secondary veins of the leaf blade branch dichotomously (two equal branches at each branch point)
    Leaf vein tips
    the veins end in small round expanded areas, and do not reach the edge of the leaf blade
    Leaflet relative size
    the bottom leaflets are about half as long as, to slightly longer than, the leaflets from the middle of the frond
    Leaflet stalks
    the leaflets are stalked
    Lobe or leaflet length
    42–166 mm
    Lobe or leaflet pairs
    10–30
    Lobe or leaflet shape
    • the lobe or leaflet is rectangular but with rounded ends (oblong)
    • the lobe or leaflet is widest below the middle and tapering at both ends; lance-shaped
    Lobe or leaflet width
    21–81 mm
    Plant growth form
    the leaves grow from a rhizome growing at or below the ground
    final leaf segment margin
    the topmost lobe or leaflet of the leaf blade has an edge with teeth tipped with bristles

  • Place

    Habitat
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • alpine or subalpine zones
    • edges of wetlands
    • forests

  • Spores or spore cones

    Sorus features
    the indusium of the sorus has glands on stalks (stipitate glands)
    Sorus shape
    the sori are circular or kidney-shaped
    Sporangia location
    the spores are clustered on sori on the lower surface of the leaf blade
    Sporangium type
    the sporangia are opaque without an annulus and usually without a stalk (leptosporangiate)
    Spore forms
    there is only one type of spore present

Wetland status

Occurs in wetlands or non-wetlands. (Wetland indicator code: FAC)

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
present
Vermont
present

Conservation status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
widespread (S-rank: S5)

From Flora Novae Angliae dichotomous key

8.  Dryopteris intermedia (Muhl. ex Willd.) Gray N

evergreen wood fern. Aspidium intermedium Muhl. ex Gray; Dryopteris austriaca (Jacq.) Woynar ex Schinz & Thellung var. intermedia (Muhl. ex Willd.) Morton; D. spinulosa (O.F. Muell.) Watt var. intermedia (Muhl. ex Willd.) Underwood • CT, MA, ME, NH, RI, VT. Forests, including rocky and high-elevation types, edges of forested wetlands. Dryopteris intermedia and 
 D. carthusiana often grow together and are sometimes confused. In addition to those characters stated in the key, the two species can often be separated merely by examining 
the orientation of the marginal teeth. Those of D. intermedia are ± outward pointing, 
whereas those of D. carthusiana are ± forward pointing.

1×8. Dryopteris campyloptera × Dryopteris intermedia → This very rare (or possibly very overlooked) wood fern hybrid is known from VT. It is identified by its intermediate morphology.

2×8. Dryopteris carthusiana × Dryopteris intermedia → Dryopteris ×‌triploidea Wherry is an uncommon wood fern hybrid known 
from CT, MA, ME, NH, RI, VT. It shows long, often outward pointed, basiscopic leafules on the lower leaflets and ± forward-curving teeth (similar to D. carthusiana), but the 
indusia (and often the rachis and costae) have stipitate glands, and the leaf blades 
are somewhat evergreen.

3×8. Dryopteris clintoniana × Dryopteris intermedia → Dryopteris ×‌dowellii (Farw.) Wherry is an infrequent wood fern hybrid known from CT, MA, ME, NH, VT. It resembles D. ×boottii (4 ×8) in many features but has broader leaf blades with a more abrupt taper at the apex.

4×8. Dryopteris cristata × Dryopteris intermedia → Dryopteris ×‌boottii (Tuckerman) Underwood is a relatively common wood fern hybrid known from CT, MA, ME, NH, RI, VT. It shows stipitate glands on the indusia (and often the rachis and costae), mostly 2.5 times divided leaf blades with ± parallel margins, triangular lower leaflets, and sori positioned midway between midvein and margin.

7×8. Dryopteris goldiana × Dryopteris intermedia → This rare wood fern hybrid is known from CT, MA, VT. Overall, the nothospecies appears closer to Dryopteris intermedia on superficial examination. However, it has scales on the petiole that are dark chestnut-brown with broad, paler brown margins (rather than lacking a dark central area as in D. intermedia). The hybrid is further characterized by leaf blades that are 2.5- to 3-times pinnately compound and mostly 1.8–2.2 times as long as wide (rather than mostly 1.7–2.2 in D. goldiana and mostly 2.3–2.6 in D. intermedia), sori positioned in 1 or more rows along each side of the leafule or lobe (rather than 1 row on each side in D. goldiana and 2 or more rows on each side in D. intermedia), and indusia with stipitate-glands (glands lacking in D. goldiana and present in D. intermedia).

8×9. Dryopteris intermedia × Dryopteris marginalis → This is a relatively rare wood fern hybrid known from CT, MA, VT. It shows sori positioned closer to the margin than the midrib of the ultimate segments and fairly dense scales at the base of the petiole (as with other D. marginalis hybrids). The 
indusia (and often the rachis and costae) have stipitate glands, and the segment margins are serrate (unlike D. marginalis).

Native to North America?

Yes

Sometimes confused with

Dryopteris carthusiana:
first lower leafule on lower leaflet as long as or longer than adjacent leafule and rachis and midrib of leaflets and leafules without stipitate glands (vs. D. intermedia, with the first lower leafule on lower leaflet shorter than the adjacent leafule and rachis and midrib of leaflets and leafules with stipitate glands).
Dryopteris campyloptera:
first lower leafule on lower leaflet as long as or longer than adjacent leafule and rachis and midrib of leaflets and leafules without stipitate glands (vs. D. intermedia, with the first lower leafule on lower leaflet shorter than the adjacent leafule and rachis and midrib of leaflets and leafules with stipitate glands).

Synonyms

  • Aspidium intermedium Muhl. ex Gray
  • Dryopteris austriaca (Jacq.) Woynar ex Schinz & Thellung var. intermedia (Muhl. ex Willd.) Morton
  • Dryopteris spinulosa (O.F. Muell.) Watt var. intermedia (Muhl. ex Willd.) Underwood

Family

Dryopteridaceae

Genus

Dryopteris