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Bolboschoenus fluviatilis — river tuber-bulrush

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New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Facts

River tuber-bulrush is threatened by influx into waterways of nutrients from, for example, fertilizers or sewage, since the higher nutrient levels increase the success of non-native plants.

Habitat

Fresh tidal marshes or flats, marshes, shores of rivers or lakes, wetland margins (edges of wetlands)

Characteristics

Habitat
  • aquatic
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
Stem shape in cross-section
the stem is roughly triangular in cross-section
Leaf blade width
7–22 mm
Leaf blade cross-section
the leaf blade is flat or rolled in at the edges
Inflorescence position
the inflorescence is at the tip of the plant
Inflorescence branching
the inflorescence is branched
Fruit type (general)
the fruit is like a seed, and surrounded by scales
Fruit length
3.8–5.5 mm
Leaf position on plant
some leaf attachment points are above the midpoint of the stem
Perianth composition
there are bristles attached at the base of the achene
Fruit cross-section
the fruit is triangular to terete (circular) in cross-section
Show all characteristics

  • Flowers

    Anther color (dry)
    the anthers range in color from white to tan or yellow to yellow-brown
    Anther length
    2.5–4.5 mm
    Floral bristle color
    the bristles are pale brown to brown
    Floral bristle number
    5-7
    Floral bristle relative length
    the bristles are between one tenth as long as the achene, and equal in length to the achene
    Floral bristles
    the bristles are straight or slightly curved
    Floral scale hairs
    the floral scales have hairs on them
    Floral scale length
    7–10 mm
    Floral scale nerves
    1
    Floral scale shape
    • the floral scales are lanceolate (widest below the middle, and tapering at both ends)
    • the floral scales are ovate (roughly egg-shaped)
    Floral scale translucent
    the floral scales are translucent
    Inflorescence bract angle
    the bracts are angled outwards near horizontal or reflexed downwards
    Inflorescence bract number
    • there are six or more bracts per inflorescence
    • there are two to five bracts per inflorescence
    Inflorescence bract position (Sparganium)
    NA
    Inflorescence bracts
    there are at least two bracts, and they are either flat or folded or rolled in at the edges
    Inflorescence branching
    the inflorescence is branched
    Inflorescence crowding
    the inflorescence is at least somewhat spread out, with at least one branch coming from the main stem
    Inflorescence position
    the inflorescence is at the tip of the plant
    Inflorescence shape
    the aggregations within the inflorescence are roughly circular (not flattened) in cross-section
    Inflorescence type
    there are two or more flowers, spikes or flower clusters on a branched inflorescence
    Perianth composition
    there are bristles attached at the base of the achene
    Stamen number
    3
    Stigma number
    3
    Style division
    the top two thirds of the style is divided
    floral bristle barbs
    the bristles have tiny barbs on them
    plantlets budding at flower bases
    no

  • Fruits or seeds

    Achene beak length
    0.2–0.8 mm
    Achene surface texture
    the achene is smooth (it has no detectable texture)
    Achene tubercle relative width
    NA
    Achene tubercle width
    0 mm
    Capsule relative length
    NA
    Fruit cross-section
    the fruit is triangular to terete (circular) in cross-section
    Fruit length
    3.8–5.5 mm
    Fruit type (general)
    the fruit is like a seed, and surrounded by scales
    Fruit type (specific)
    the fruit is an achene (dry, seed-like fruit) without a tubercle (a swelling or projection, usually of a different color or texture)
    Locules in capsule
    NA
    Seed length
    0 mm
    Seed tail relative length
    0 mm
    Seed tails
    NA
    Tubercle height
    0 mm

  • Growth form

    Lifespan
    the plant lives more than two years
    Underground organs
    • the plant has a rhizome (a horizontal underground stem with roots growing from it)
    • the plant has one or more swollen storage organs underground, such as bulbs or tubers

  • Leaves

    Auricle length
    0 mm
    Auricle texture
    NA
    Auricles
    there are no auricles on the leaf sheath
    Leaf blade cross-section
    the leaf blade is flat or rolled in at the edges
    Leaf blade width
    7–22 mm
    Leaf form
    all the leaves hold their form out of water
    Leaf position on plant
    some leaf attachment points are above the midpoint of the stem
    Leaf septa
    the leaf blades do not have transverse septa
    Leaf sheath hairs
    the leaf sheathes are without hairs
    Pedicel length (Typha)
    0 mm
    Stem leaf blade ligules
    there are no ligules at the leaf blade bases
    Stem leaf blades
    there are fully-developed leaves with leaf blades on the main stem

  • Place

    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • edges of wetlands
    • fresh tidal marshes or flats
    • marshes
    • shores of rivers or lakes

  • Stem, shoot, branch

    Plant height
    100–200 cm
    Stem shape in cross-section
    the stem is roughly triangular in cross-section
    Stem texture near tip
    the stem feels smooth near the tip
    Stem thickness at midpoint
    5–15 mm

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

New England distribution and conservation status

Distribution

Connecticut
absent
Maine
absent
Massachusetts
absent
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.

Massachusetts
rare (S-rank: S2)

Native to North America?

Yes

Sometimes confused with

Bolboschoenus glaucus:
widest leave blades 7-22 mm wide, spikelets mostly 3-5 mm wide, and achenes 2.5-3.3 mm long with a minute style beak (vs. B. fluviatilis, with widest leaf blades 7-22 mm wide, spikelets mostly 5-10 mm in diameter, and achenes 3.8-5.5 mm long with an evident style beak 0.1-0.8 mm long).
Bolboschoenus novae-angliae:
achenes 3-4.3 mm long, usually compressed trigonous, with exocarp cellas 1.5-3 times as tall as wide, and dried or dehisced anthers dark yellow to orange-yellow (vs. B. fluviatilis, with achenes 3.8-5.5 mm long, usually equilaterally trigonous, with isodiametric exocarp cells, and dried or dehisced anthers pale yellow to pale yellow-brown).

Synonyms

  • Schoenoplectus fluviatilis (Torr.) M.T. Strong
  • Scirpus fluviatilis (Torr.) Gray
  • Scirpus maritimus L. var. fluviatilis Torr.

Family

Cyperaceae

Genus

Bolboschoenus

Help

From the dichotomous key of Flora Novae Angliae

1.  Bolboschoenus fluviatilis (Torr.) Soják n

river tuber-bulrush. Schoenoplectus fluviatilis (Torr.) M.T. Strong; Scirpus fluviatilis (Torr.) Gray; S. maritimus L. var. fluviatilis Torr. • CT, MA, ME, NH, VT. Marshes, lake shores, river shores, including fresh-tidal sections. This species is native to all states except NH, where the population was introduced in a human-made wetland planting.