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Sparganium natans — arctic bur-reed

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Facts

Arctic bur-reed is found in shallow, still or slow-moving water, including pools in peatlands. The bur-reeds can only be confidently identified when they are in flower, and they typically flower sparsely and sporadically. Arctic bur-reed is protected in some New England states.

Habitat

Bogs, fens, lacustrine (in lakes or ponds), riverine (in rivers or streams), shores of rivers or lakes

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
40–600 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
2–4 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)
    Inflorescence width
    5–12 mm
    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
    0.5–1.5 mm
    Fruit compartments
    there is only one locule in the fruit
    Fruit length
    2–4 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
    1–1.5 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
    40–600 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
    • bogs
    • fens
    • in lakes or ponds
    • in rivers or streams
    • shores of rivers or lakes

  • 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
extremely rare (S-rank: S1), endangered (code: E)
New Hampshire
rare (S-rank: S2), threatened (code: T)
Vermont
rare (S-rank: S2), threatened (code: T)

From Flora Novae Angliae dichotomous key

7.  Sparganium natans L. NC

arctic bur-reed. Sparganium minimum (Hartman) Wallr. • CT, MA, ME, NH, VT; also reported for RI by George (1992), but specimens are unknown. Shorelines, pools in peatlands, and shallow, acidic to basic, still or slow-moving water.

Native to North America?

Yes

Sometimes confused with

Sparganium americanum:
flowering stems with 4–10 or more staminate spikes, fruiting spikes 15–25 mm in diameter, and beak of achene 3–5 mm long (vs. S. natans, with flowering stems with 1 staminate spike, fruiting spikes 5–12 mm in diameter, and beak of achene 0.5–1.5 mm long).
Sparganium fluctuans:
flowering stems with 3–6 staminate spikes, fruiting spikes 15–23 mm in diameter, and beak of achene 2–3.5 mm long (vs. S. natans, with flowering stems with 1 staminate spike, fruiting spikes 5–12 mm in diameter, and beak of achene 0.5–1.5 mm long).

Synonyms

  • Sparganium minimum (Hartman) Wallr.

Family

Typhaceae

Genus

Sparganium