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Sparganium fluctuans — floating bur-reed

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Facts

Floating bur-reed has a circumboreal distribution, and it is found in New England and sparsely across northern North America. It inhabits shallow, still or slow-moving water, the strap-shaped leaves floating on the surface.

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams)

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
  • Vermont
Leaf arrangement
alternate: there is one leaf per node along the stem
Leaf blade shape
the leaf blade is linear (very narrow with more or less parallel sides)
Leaf blade length
600–1000 mm
Flower petal color
  • green to brown
  • white
Petal fusion
the perianth parts are separate
Inflorescence type
the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
Ovary position
the ovary is above the point of petal and/or sepal attachment
Fruit type (specific)
  • the fruit is a drupe (fleshy, with a firm inner ovary wall that encloses a single seed)
  • the fruit is an achene (dry, usually 1-seeded, does not separate or split open at maturity)
Fruit length
2–5 mm
Show all characteristics

  • Clonal plantlets

    Axillary bulblets
    there are no bulblets being produced in axils

  • Flowers

    Anther attachment
    the anther is attached by its base to the filament
    Bulblets replace flowers
    there are no bulblets where the flowers are located
    Carpels fused
    the carpel is solitary or (if 2 or more) the carpels are not fused to one another
    Flower petal color
    • green to brown
    • white
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Fringed petal edges
    the petals are not fringed
    Hairs on flower stalk
    NA
    Inflorescence type
    the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
    Marks on petals
    there are no noticeable marks on the petals
    Nectar spur
    the flower has no nectar spurs
    Number of pistils
    1
    Number of styles
    1
    Ovary position
    the ovary is above the point of petal and/or sepal attachment
    Petal appearance
    the petals are green and/or leafy in texture
    Petal fusion
    the perianth parts are separate
    Sepal appearance
    the sepals resemble leaves in color and texture
    Sepals fused only to sepals
    the sepals are separate from one another
    Spathe
    the plant does not have a spathe
    Spathe form
    NA
    Stamen number
    • 1 or 2
    • 3
    • 4
    • 5
    • 6
    • 7
    • 8
    Stamen position relative to petals
    NA
    Stamens fused
    the stamens are fused to one another at or near their bases
    Stamens fused outwards
    the stamens are not fused to the petals or tepals
    Style petal-like
    the style is not broad and flattened like a petal
    Tepals
    the petals and sepals are similar in size and color

  • Fruits or seeds

    Berry color
    NA
    Capsule ridges
    NA
    Fruit beak length
    2–3.5 mm
    Fruit compartments
    there is only one locule in the fruit
    Fruit length
    2–5 mm
    Fruit type (general)
    the fruit is dry but does not split open when ripe
    Fruit type (specific)
    • the fruit is a drupe (fleshy, with a firm inner ovary wall that encloses a single seed)
    • the fruit is an achene (dry, usually 1-seeded, does not separate or split open at maturity)
    Fruit width
    1.5–2 mm
    Other markings on berry
    NA

  • Glands or sap

    Sap
    the sap is clear and watery

  • 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)

  • Leaves

    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade basal lobes
    the leaf blades do not have basal lobes
    Leaf blade base
    the leaf has no stalk
    Leaf blade base shape
    the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow
    Leaf blade cross-section
    • the leaf blade is U- or V-shaped
    • the leaf blade is more or less flat in cross-section
    Leaf blade faces
    both surfaces of the leaf blade are exposed
    Leaf blade form
    Fully-formed (i.e., expanded), +/- green leaf blades are found somewhere on the plant
    Leaf blade length
    600–1000 mm
    Leaf blade shape
    the leaf blade is linear (very narrow with more or less parallel sides)
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets
    Stipule twining
    NA
    Stipules
    there are no stipules on this plant

  • Place

    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • in lakes or ponds
    • in rivers or streams

  • Scent

    Plant odor
    the leaves have no particular smell

  • Stem, shoot, branch

    Flowering stem leaves
    there is at least one fully-formed leaf on the flowering stem

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
absent
Vermont
present

Conservation status

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

Connecticut
extremely rare (S-rank: S1), endangered (code: E)
Massachusetts
rare to uncommon (S-rank: S2S3)
Vermont
uncommon (uncertain) (S-rank: S3?)

From Flora Novae Angliae dichotomous key

6.  Sparganium fluctuans (Morong) B. L. Robins. N

floating bur-reed. CT, MA, ME, NH, VT. Shallow, circumneutral, still or slow-moving water. The leaves of Sparganium fluctuans are flaccid and unkeeled, as in S. angustifolium. In addition to the differences noted in the key, these two species can also be separated by the inflorescence architecture. Sparganium fluctuans frequently has at least one inflorescence branch bearing 2 or more spikes (vs. all spikes solitary, even if borne on a peduncle), and the staminate spikes are usually not contiguous (vs. contiguous).

Native to North America?

Yes

Sometimes confused with

Sparganium angustifolium:
beak of mature fruit +/- terete, straight or only slightly curved, tepals free from fruit stipe, and anthers 0.8–1.5 mm long (vs. S. fluctuans, with beak of mature fruit flattened and strongly curved, tepals adnate to fruit stipe for ca. 1/2 their length, and anthers mostly 0.6–0.7 mm long).
Sparganium emersum:
beak of mature fruit +/- terete, straight or only slightly curved, tepals free from fruit stipe, and anthers 0.8–1.5 mm long (vs. S. fluctuans, with beak of mature fruit flattened and strongly curved, tepals adnate to fruit stipe for ca. 1/2 their length, and anthers mostly 0.6–0.7 mm long).

Family

Typhaceae

Genus

Sparganium