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Osmunda claytoniana — interrupted fern

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Facts

Interrupted fern is very common throughout New England. It gets its common name from the distinct interruptions present in the center of many fronds, caused by the fertile pinnae (leaflets).

Habitat

Forests, shores of rivers or lakes, swamps, 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 compound (divided into leaflets)
  • 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 slightly different from the sterile fronds
Sorus shape
there are no sori, or they are concealed in leaf segments or hardened, capsule-like structures derived from a modified leaflet
Leaf stalk scales
there are no scales on the leaf stalk
Leaf stalk hairs
  • the leaf stalk has hairs
  • there are no hairs on the leaf stalk
Leaf blade length
45–90 cm
Leaf vein tips
the veins go all the way to 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 slightly different from the sterile fronds

  • Leaves

    Features of leaves
    there are no special features on the leaves
    Leaf blade length
    45–90 cm
    Leaf blade shape
    • the leaf blades are longer than wide, with roughly parallel sides (oblong)
    • the leaf blades are widest near the middle and tapered towards the base and tip (elliptic)
    Leaf blade tip shape
    the tip of the leaf blade is rounded
    Leaf blade width
    At least 15 cm
    Leaf divisions
    • the leaf blade is compound (divided into leaflets)
    • the leaf blade is twice compound (divided into leaflets, which are further divided into leaflets)
    Leaf lifespan
    the leaves drop off in winter
    Leaf stalk color
    • green
    • yellow to brown
    Leaf stalk hairs
    • the leaf stalk has hairs
    • there are no hairs on the leaf stalk
    Leaf stalk length
    106–533 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
    there are no scales on the leaf stalk
    Leaf stalk scales
    there are no scales on the leaf stalk
    Leaf stalk vessels
    1 bundle, U-shaped
    Leaf vein branching
    the secondary veins of the leaf blade branch dichotomously (two equal branches at each branch point)
    Leaf vein tips
    the veins go all the way to 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
    • the leaflets do not have stalks
    Lobe or leaflet length
    60–150 mm
    Lobe or leaflet pairs
    10–25
    Lobe or leaflet shape
    the lobe or leaflet is rectangular but with rounded ends (oblong)
    Lobe or leaflet width
    20–30 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 a smooth or lobed edge

  • Place

    Habitat
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of wetlands
    • forests
    • shores of rivers or lakes
    • swamps

  • Spores or spore cones

    Sorus features
    there are no special features on the sorus
    Sorus shape
    there are no sori, or they are concealed in leaf segments or hardened, capsule-like structures derived from a modified leaflet
    Sporangia location
    the spores cover the surfaces of modified leaves or leaflets
    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

1.  Osmunda claytoniana L. N

interrupted fern. CT, MA, ME, NH, RI, VT; throughout and common. Mesic to hydric soils of forests, swamps, and shorelines.

1×2. Osmunda claytoniana × Osmunda regalis → Osmunda ×‌ruggii R. Tryon is an extremely rare fern hybrid known from CT 
 (only two populations, CT and VA, reported from the world by Whetstone and Atkinson 1993). Only vegetative leaves have been seen in the wild. These are twice pinnately divided with sessile leafules (the leaflets of O. regalis are short-stalked). The report 
of O. ×‌ruggii from NH by Thorne and Thorne (1989) requires confirmation (photos are stored at VT).

Native to North America?

Yes

Sometimes confused with

Osmundastrum cinnamomeum:
spores borne on separate, fertile leaves and vegetative leaves with a tuft of light red-brown hairs at the base of the leaflets (vs. O. claytoniana, with spores borne on fertile leaflets near middle of leaf blade and leaflets on vegetative leaves lacking a prominent tuft of light red-brown hairs at the base of the leaflets).

Family

Osmundaceae

Genus

Osmunda