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

Stuckenia filiformis — thread-leaved false pondweed

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Facts

Thread-leaved false pondweed is rare in New England, being found only in the northern portions of Maine, New Hampshire and Vermont. This species has traditionally been considered divided into two subspecies in New England based on larger more robust, but sterile plants in moving water and smaller, fertile plants in still water. But transplant studies contradict this, showing that most of this variation is environmental rather than genetic

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
New England state
  • Maine
  • New Hampshire
  • Vermont
Leaf position
the leaves are all submerged underwater
Leaf arrangement
alternate: there is one leaf per node along the stem
Leaf blade length
10–150 mm
Petal or sepal number
there are four petals, sepals, or tepals in the flower
Specific leaf type
the leaf is not divided, rather the blade is made up of one segment
Floating leaf shape
NA
Underwater leaf blade width
0.2–5 mm
Fruit type (general)
the fruit is fleshy
Underwater leaf length
10–150 mm
Show all characteristics

  • Clonal plantlets

    Turion length
    0 mm

  • Flowers

    Carpels fused
    the carpel is solitary or (if 2 or more) the carpels are not fused to one another
    Flower lower lip length
    0 mm
    Flower number
    2–12
    Flower position
    the flowers are below the surface of the water
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Inflorescence length
    5–55 mm
    Inflorescence type
    the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
    Length of peduncle
    20–150 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    4
    Ovary position
    the sepals and/or petals are attached below the ovary
    Palate on corolla
    no
    Petal and sepal arrangement
    the flower includes only one cycle of petals or sepals
    Petal appearance
    the petals are green and/or leafy in texture
    Petal fringed edges
    the petals are not fringed
    Petal fusion
    the perianth parts are separate
    Petal hairs on inner/upper surface
    there are no hairs on the inner/upper petal surface
    Petal length
    0.5–1 mm
    Petal number
    4
    Petal or sepal number
    there are four petals, sepals, or tepals in the flower
    Pistil number
    4
    Sepal appearance
    NA
    Sepal length
    0 mm
    Sepal number
    0
    Sepals fused only to sepals
    NA
    Spur length
    0 mm
    Stamen number
    • 1 or 2
    • 4
    Stamen position relative to petals
    NA
    Stamens fused to petals
    the stamens are fused near the bases of the petals or tepals
    Style number
    4

  • Fruits or seeds

    Fruit beak length
    0.3 mm
    Fruit length
    2–3 mm
    Fruit type (general)
    the fruit is fleshy
    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
    1.5–2.4 mm

  • Glands or sap

    Oil glands on nodes
    none of the nodes have oil glands
    Sap
    the sap is clear and watery

  • Growth form

    Lifespan
    the plant lives more than two years
    Root septa
    the roots do not have transverse septa
    Roots floating in water
    there are no clusters of roots floating in the water
    Turions
    there are no turions on the plant
    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, tubers or corms

  • Leaves

    Bract position (Sparganium)
    NA
    Bract relative length
    At least 3854 mm
    Bracts
    neither the flowers nor their pedicels have bracts
    Floating leaf basal lobes
    NA
    Floating leaf blade width
    0 mm
    Floating leaf length
    0 mm
    Floating leaf shape
    NA
    Floating leaf tip
    NA
    Floral bract form
    NA
    Floral bract length
    0 mm
    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade length
    10–150 mm
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf blade width
    0.2–5 mm
    Leaf position
    the leaves are all submerged underwater
    Leaf special features
    none of the mentioned special features are present
    Leaf-like branch segments
    0
    Leaf-like branch shape
    NA
    Specific leaf type
    the leaf is not divided, rather the blade is made up of one segment
    Staminate bract edge (Myriophyllum)
    NA
    Stipule appearance
    the stipules are delicate and translucent
    Stipule fused to leaf
    the stipules are attached to the leaf blade for some part of their length
    Stipules
    there are no stipules on the plant
    Stipules fused around stem
    the stipules form a completely closed tube around the stem
    Trap-bladder length
    0 mm
    Underwater leaf air passage number
    At least 1439
    Underwater leaf air passage relative width
    At least 4336
    Underwater leaf air passage row number
    0
    Underwater leaf blade edges
    the underwater leaf has smooth edges, without teeth
    Underwater leaf blade shape
    the underwater leaf blade is linear (very narrow with more or less parallel sides)
    Underwater leaf blade veins
    1–3
    Underwater leaf blade width
    0.2–5 mm
    Underwater leaf length
    10–150 mm
    Underwater leaf stalk
    no
    Underwater leaf stalk length
    0 mm
    Underwater leaf tip shape
    • the tip of the underwater leaf is obtuse (bluntly pointed)
    • the tip of the underwater leaf is truncate (ends abruptly in a more or less straight line as though cut off)
    Veins in floating leaf
    0

  • Place

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

  • Stem, shoot, branch

    Flowering stem growth form
    the flowering stem trails along the substrate, or floats in the water

Wetland status

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

In New England

Distribution

Connecticut
absent
Maine
present
Massachusetts
absent
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.

Maine
extremely rare (S-rank: S1)
New Hampshire
historical (S-rank: SH), endangered (code: E)
Vermont
extremely rare (S-rank: S1)

ssp. alpinus

Maine
rare (S-rank: S2), special concern (code: SC)

ssp. occidentalis

Maine
extremely rare (S-rank: S1)

From Flora Novae Angliae dichotomous key

1.  Stuckenia filiformis (Pers.) Boerner NC

thread-leaved false pondweed. Coleogeton filiformis (Pers.) D. Les & R. Haynes ssp. alpinus (Blytt) D. Les & R. Haynes; C. filiformis (Pers.) D. Les & R. Haynes ssp. occidentalis (J.W. Robbins) D.H. Les & Haynes; Potamogeton filiformis Pers. var. alpinus (Blytt) Aschers. & Graebn.; 
 P. filiformis Pers. var. borealis (Raf.) St. John; P. filiformis Pers. var. macounii Morong; P. filiformis Pers. var. occidentalis (J.W. Robbins) Morong; Stuckenia filiformis (Pers.) Börner ssp. alpina (Blytt) Haynes, D.H. Les, & M. Kral; S. filiformis (Pers.) Börner ssp. occidentalis (J.W. Robbins) Haynes, D.H. Les, & M. Kral • ME, NH, VT; northern portion of states. Shallow, still or slow-moving, circumneutral to basic water of lakes and rivers. Two infraspecific taxa have traditionally been recognized in New England—a robust plant with broader leaves and sterile fruits most commonly found in moving water ( occidentalis) and a smaller plant with narrower leaves and fertile fruits from still and slow-moving water ( alpina). Various studies, including transplant experiments, show that much of the variation observed in Stuckenia filiformis is under environmental control (Kaplan 2008), including leaf width, stem length, and fruit production. Given these facts and other complications (e.g., the epithet alpina is based on a European type but is applied only to plants from North America and Asia by Haynes and Hellquist 2000c), S. filiformis is recognized here in the broad sense without infraspecific taxa. Note that the more robust, moving-water forms are responsible for reports of Stuckenia vaginata (Turcz.) Holub from New England (e.g., Magee and Ahles 1999).

1×S. vaginata (Turcz.) Holub. Stuckenia filiformis × Stuckenia vaginata (Turcz.) Holub → Stuckenia ×‌fennica (Hagstr.) Holub is a very rare false pondweed hybrid in New England known from ME and VT. It is responsible for reports of Stuckenia filiformis ssp. ‌occidentalis in New England. The hybrid is a riverine species that rarely forms fruits. It has leaf blades mostly 0.5-2 mm wide, with stipules on the proximal portion of the plant loose, inflated, mostly 0.2-5 mm wide, disintegrating in age (vs. Stuckenia filiformis, with leaf blades mostly 0.2-0.8 mm wide, with stipules on the proximal portion of the plant tightly clasping, 0.2-1 mm wide, persistent in age).

Native to North America?

Yes

Sometimes confused with

Stuckenia pectinata:
stipular sheaths open with overlapping edges, leaf blades commonly acute at the apex, with an apiculus on young plants, and drupes 3–4.5 mm long, with a tiny beak (vs. S. filiformis, with stipular sheaths closed, leaf blades commonly blunt to obtuse at the apex, sometimes retuse, rarely apiculate, and drupes 2–3 mm long, beakless).

Synonyms

  • Coleogeton filiformis (Pers.) D. Les & R. Haynes ssp. alpinus (Blytt) D. Les & R. Haynes
  • Coleogeton filiformis (Pers.) D. Les & R. Haynes ssp. occidentalis (J.W. Robbins) D.H. Les & Haynes
  • Potamogeton filiformis Pers. var. alpinus (Blytt) Aschers. & Graebn.
  • Potamogeton filiformis Pers. var. macounii Morong
  • Potamogeton filiformis Pers. var. occidentalis (J.W. Robbins) Morong
  • Stuckenia filiformis (Pers.) Börner ssp. alpina (Blytt) Haynes, D.H. Les, & M. Kral
  • Stuckenia filiformis (Pers.) Börner ssp. occidentalis (J.W. Robbins) Haynes, D.H. Les, & M. Kral

Family

Potamogetonaceae

Genus

Stuckenia