Your help is appreciated. We depend on donations to help keep this site free and up to date for you. Can you please help us?

Donate

Native Plant Trust: Go Botany Discover thousands of New England plants

Carex vacillans — swinging sedge

Copyright: various copyright holders. To reuse an image, please click it to see who you will need to contact.

Facts

Swinging sedge is an unusual case of a stable, fertile hybrid between smooth black sedge (Carex nigra, a sedge of wet meadows) and chaffy sedge (C. paleacea, a salt marsh sedge). There is another stable hybrid sedge that shares one parent with swinging sedge, estuary sedge (C. recta). The two hybrid species are very similar to one another, and can only be distinguished with careful study. Swinging sedge is rare, and occurs in saline and brackish marshes and coastal shorelines in Maine and Massachusetts.

Habitat

Brackish or salt marshes and flats, intertidal, subtidal or open ocean, shores of rivers or lakes

New England distribution

Adapted from BONAP data

Found this plant? Take a photo and post a sighting.

North America distribution

Adapted from BONAP data

enlarge

Characteristics

Habitat
  • terrestrial
  • wetlands
New England state
  • Maine
  • Massachusetts
stem leaf blade width
2.8–4 mm
Lowest bract sheath
the lowest bract has no sheath (or a very short sheath up to four millimeters in length)
Spike on stalk
the lowest spike on the plant has a peduncle
Top spike
the uppermost spike contains only staminate flowers
Perigynium hairs
the perigynium has no hairs
Perigynium length
2.5–3.3 mm
Leaf sheath color
the leaf sheath has no pink, red or purple tinting
Leaf blade texture
the leaf blade is smooth and hairless, or rough and sandpapery
Perigynium beak teeth
the perigynium beak is not divided at the tip into two teeth, or the teeth are very tiny
Show all characteristics

  • Flowers

    Bumps on fruit
    the perigynium surface has papillae on it
    Length of scale
    • the scale is nearly as long as, or longer than, the perigynium
    • the scale is shorter than the perigynium
    Lowest spike length
    28–50 mm
    Lowest spike stalk length
    6–17 mm
    Lowest spike width
    5–7 mm
    Perigynium beak
    the perigynium has a beak
    Perigynium beak length
    0.1–0.3 mm
    Perigynium beak orientation
    the beak of the perigynium is straight, and in line with the perigynium
    Perigynium beak serrations
    • the perigynium beak has no serrations
    • the perigynium beak has tiny serrations along the edges
    Perigynium beak teeth
    the perigynium beak is not divided at the tip into two teeth, or the teeth are very tiny
    Perigynium beak teeth length
    0 mm
    Perigynium color
    tan
    Perigynium cross-section
    • the perigynium is biconvex (convexly rounded on both sides, like a lens) in cross-section
    • the perigynium is planoconvex (flat on one surface and rounded on the other) in cross-section
    Perigynium hairs
    the perigynium has no hairs
    Perigynium length
    2.5–3.3 mm
    Perigynium nerve number
    4–10
    Perigynium nerve texture
    the nerves on the perigynium are raised, even after drying the perigynium
    Perigynium nerves lower side
    2–5
    Perigynium nerves upper side
    2–5
    Perigynium orientation
    the perigynia are oriented vertically or pressed against the axis or adjacent perigynia
    Perigynium puffy
    the perigynium is inflated (there is space between the perigynium and the achene)
    Perigynium shape
    • the perigynium body is elliptic (widest near the middle and tapering at both ends)
    • the perigynium body is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    Perigynium width
    1.5–2.2 mm
    Perigynium winged
    the perigynium has no wings
    Pollen- and seed-producing spikes
    some of the spikes produce perigynia
    Pollen-producing spike number
    1–3
    Scale awn
    the carpellate scale has an awn on it
    Scale awn texture
    the carpellate scale awn has tiny teeth
    Scale color
    • brown
    • purple to black
    Scale length
    2.5–5.5 mm
    Scale tip
    the carpellate scale tip is acuminate (tapered to a narrow point)
    Spike on stalk
    the lowest spike on the plant has a peduncle
    Spike orientation
    • the spikes are bent downwards or droop downwards
    • the spikes are oriented vertically or pressed against the axis
    Spikes per stem
    2-15
    Stigma branching
    the stigmas have two branches
    Top spike
    the uppermost spike contains only staminate flowers

  • Fruits or seeds

    Achene dimples
    • the achene has a clear fold or dimple
    • the achene has no folds or dimples
    Style persistence
    the style falls off the mature achenes

  • Leaves

    Leaf arrangement
    the leaves are all produced from the base of the plant
    Leaf blade texture
    the leaf blade is smooth and hairless, or rough and sandpapery
    Leaf bumps
    • the upper surface of the leaf blade does not have papillae
    • the upper surface of the leaf blade has papillae on it
    Leaf sheath bumps
    there are no papillae at the top edge of the leaf sheath
    Leaf sheath color
    the leaf sheath has no pink, red or purple tinting
    Leaf sheath dots
    there are no dots on the leaf sheathes
    Leaf sheath folds
    there are no corrugations on the leaf sheath
    Leaf sheath texture
    the leaf sheath feels smooth, and has no hairs
    Lowest bract sheath
    the lowest bract has no sheath (or a very short sheath up to four millimeters in length)
    Lowest leaf blade width
    2.8–4 mm
    Lowest leaf sheath texture
    the leaf sheath feels smooth (it may have soft hairs)
    stem leaf blade width
    2.8–4 mm

  • Place

    Habitat
    • terrestrial
    • wetlands
    New England state
    • Maine
    • Massachusetts
    Specific habitat
    • brackish or salt marshes and flats
    • intertidal, subtidal or open ocean
    • shores of rivers or lakes

  • Stem, shoot, branch

    Plant height
    15–60 cm
    Relative stem height
    the main stem is taller than the leaves
    Stem cross-section
    the main stem is roughly triangular in cross-section
    Stem spacing
    the stems grow singly or a few together (they may form diffuse colonies)

Wetland status

Not classified

In New England

Distribution

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

Conservation status

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

Maine
rare (S-rank: S2), endangered (code: E)
Massachusetts
historical (S-rank: SH), H (code: H)

From Flora Novae Angliae dichotomous key

143.  Carex vacillans Drej. ex Hartman NC

swinging sedge. Carex ×‌super-goodenoughii (Kükenth.) Lepage • MA, ME. Saline and brackish marshes, Atlantic coast shorelines, tidal river shores. Most (and perhaps all) of the recent reports of this species in MA (e.g., Standley et al. 2002) are based on Carex paleacea ×C. stricta.

Native to North America?

Yes

Sometimes confused with

Carex recta:
perigynia short-papillose, veinless or obscurely veined and and carpellate scales bronze to brown with a paler central band that is 33-50% the total width of the scale (vs. C. vacillans, with perigynia long-papillose, with 2-5 veins on each surface and carpellate scales dark brown to purple-brown with a paler central band that is 10-33% the total width of the scale).

Synonyms

  • Carex ×‌super-goodenoughii (Kükenth.) Lepage

Family

Cyperaceae

Genus

Carex