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Bolboschoenus robustus — sea-coast tuber-bulrush

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Facts

Sea-coast tuber-bulrush is native to brackish and saline coastal shorelines and marshes in New England; it is considered rare in New Hampshire and Vermont. However, this widespread species extends throughout the Atlantic and southeastern states west to Texas and California. Muskrat and waterfowl, including geese, eat its seeds. Spreading by rhizomes, this species is a pioneer on exposed muds. It flowers between April and August, and fruits between July and October.

Habitat

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

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
  • aquatic
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
Stem shape in cross-section
the stem is roughly triangular in cross-section
Leaf blade width
4–12 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
  • the inflorescence is on one or more stems with no branches
Fruit type (general)
the fruit is like a seed, and surrounded by scales
Fruit length
2.7–3.5 mm
Leaf position on plant
  • some leaf attachment points are above the midpoint of the stem
  • the attachment points of all the leaves are at or near the base of the plant
Perianth composition
there are bristles attached at the base of the achene
Fruit cross-section
  • the fruit is biconvex or elliptic (widest in the middle and tapering to both ends) in cross-section
  • the fruit is triangular to terete (circular) in cross-section
Show all characteristics
  • Flowers

    Anther color (dry)
    the anthers are orange to red-brown in color
    Anther length
    1.5–2.5 mm
    Floral bristle color
    the bristles are slightly or strongly colored with reddish brown
    Floral bristle number
    • 0
    • 1-4
    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
    6–9 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 opaque
    Inflorescence bract angle
    the bracts are vertical or angled only slightly outwards
    Inflorescence bract number
    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
    • the inflorescence is on one or more stems with no branches
    Inflorescence crowding
    the inflorescence is crowded together in one tight cluster
    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
    • 2
    • 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
    0.1–0.3 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 biconvex or elliptic (widest in the middle and tapering to both ends) in cross-section
    • the fruit is triangular to terete (circular) in cross-section
    Fruit length
    2.7–3.5 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
    Rhizome thickness
    3–4 mm
    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 length
    50–600 mm
    Leaf blade width
    4–12 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
    • the attachment points of all the leaves are at or near the base of the plant
    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
    Width of seed-producing inflorescence
    8–12 mm
  • Place

    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    Specific habitat
    • brackish or salt marshes and flats
    • fresh tidal marshes or flats
    • intertidal, subtidal or open ocean
    • shores of rivers or lakes
    • swamps
  • Stem, shoot, branch

    Plant height
    50–150 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

Wetland status

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

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
present
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), special concern (code: SC)

From Flora Novae Angliae dichotomous key

5.  Bolboschoenus robustus (Pursh) Soják N

sea-coast tuber-bulrush. Schoenoplectus robustus (Pursh) M.T. Strong; Scirpus maritimus L. var. macrostachyus Michx.; S. robustus Pursh • CT, MA, ME, NH, RI. Brackish to saline coastal shorelines and marshes.

3×5. Bolboschoenus maritimus × Bolboschoenus robustus This rare tuber-bulrush hybrid is frequently encountered when both parent species are sympatric. It is known from CT, MA, ME, NH, RI. It is similar to both parents 
but shows dark yellow to orange-yellow anthers and barely translucent scales.

Native to North America?

Yes

Sometimes confused with

Bolboschoenus maritimus

Synonyms

  • Schoenoplectus robustus (Pursh) M.T. Strong
  • Scirpus maritimus L. var. macrostachyus Michx.
  • Scirpus robustus Pursh

Family

Cyperaceae