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Potamogeton epihydrus — ribbon-leaved pondweed

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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

Ribbon-leaved pondweed is a common species throughout the northern United States and southern Canada, and it is found throughout New England. The submersed leaves are narrow and ribbon-like, thin and transparent, with prominent bands of lacunar cells 1–2 mm wide on each side of the midrib. The floating leaves are broad and elliptical.

Habitat

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

Characteristics

Habitat
aquatic
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf position
  • some of the leaves are floating at the surface of the water
  • the leaves are all submerged underwater
Leaf arrangement
alternate: there is one leaf per node along the stem
Leaf blade length
20–220 mm
Petal or sepal number
there are four petals, sepals, or tepals in the flower
Petal color
green
Specific leaf type
the leaf is not divided, rather the blade is made up of one segment
Floating leaf shape
  • the leaf blade is elliptic (widest near the middle and tapering at both ends)
  • the leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the leaf blade)
  • the leaf blade is oblong (rectangular but with rounded ends)
Underwater leaf blade width
1–10 mm
Fruit type (general)
  • the fruit is dry but does not split open when ripe
  • the fruit is fleshy
Underwater leaf length
50–220 mm
Show all characteristics

  • Clonal plantlets

    Turion length
    0 mm

  • Flowers

    Anther color
    there is a noticeable pink, reddish or purplish tint to the anthers
    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 position
    the flowers are above 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
    8–40 mm
    Inflorescence type
    the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
    Length of flower stalk
    0 mm
    Length of peduncle
    15–160 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    1–4
    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 color
    green
    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
    1.5–3 mm
    Petal number
    4
    Petal or sepal number
    there are four petals, sepals, or tepals in the flower
    Pistil number
    • 1
    • 4
    Sepal appearance
    NA
    Sepal length
    0 mm
    Sepal number
    0
    Sepals fused only to sepals
    NA
    Spur length
    0 mm
    Stamen number
    4
    Stamen position relative to petals
    NA
    Stamens fused
    the stamens are not fused to one another
    Stamens fused to petals
    the stamens are fused near the bases of the petals or tepals
    Style number
    0–4

  • Fruits or seeds

    Fruit beak length
    0.5 mm
    Fruit length
    2.5–4.5 mm
    Fruit type (general)
    • the fruit is dry but does not split open when ripe
    • 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
    2–3.6 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)

  • 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
    no
    Floating leaf blade width
    4–20 mm
    Floating leaf length
    20–80 mm
    Floating leaf shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the leaf blade)
    • the leaf blade is oblong (rectangular but with rounded ends)
    Floating leaf tip
    the tip of the floating leaf blade is rounded, with no point
    Floral bract form
    NA
    Floral bract length
    0 mm
    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade length
    20–220 mm
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf blade width
    1–20 mm
    Leaf position
    • some of the leaves are floating at the surface of the water
    • 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 firm or fibrous, and colored white, green or brown
    Stipule fused to leaf
    the stipules are not attached to the leaf blade at all
    Stipules
    the plant has stipules
    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 1440
    Underwater leaf air passage relative width
    At least 1442
    Underwater leaf air passage row number
    9–18
    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
    3–13
    Underwater leaf blade width
    1–10 mm
    Underwater leaf length
    50–220 mm
    Underwater leaf stalk
    no
    Underwater leaf stalk length
    0 mm
    Underwater leaf tip shape
    • the tip of the underwater leaf is acute (sharply pointed)
    • the tip of the underwater leaf is obtuse (bluntly pointed)
    • the tip of the underwater leaf is rounded, with no point
    Veins in floating leaf
    11–41

  • Place

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

  • Stem, shoot, branch

    Flowering stem growth form
    the flowering stem is upright

Wetland status

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

New England distribution and conservation status

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
present
Vermont
present

Conservation status

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

Massachusetts
widespread (S-rank: S5)

Native to North America?

Yes

Sometimes confused with

Potamogeton zosteriformis:
floating leaves always absent and submersed leaves with 15-25 veins, lacking lacunae (vs. P. epihydrus, with floating leaves usually produced on some plants and submersed leaves with 3-13 veins, with prominent bands of lacunae on each side of the midrib).

Synonyms

  • Potamogeton epihydrus var. nuttallii (Cham. & Schlecht.) Fern.
  • Potamogeton epihydrus var. ramosus (Peck) House

Family

Potamogetonaceae

Genus

Potamogeton

Help

From the dichotomous key of Flora Novae Angliae

7.  Potamogeton epihydrus Raf. N

ribbon-leaved pondweed. Potamogeton epihydrus Raf. var. nuttallii (Cham. & Schlecht.) Fern.; P. epihydrus Raf. var. ramosus (Peck) House • CT, MA, ME, NH, RI, VT; throughout. Shallow, still or slow-moving, acidic to basic water of lakes and rivers.

4×7. Potamogeton bicupulatus × Potamogeton epihydrus → Potamogeton ×‌aemulans Z. Kaplan, Hellquist, & Fehrer is a rare pondweed hybrid responsible for reports of Potamogeton diversifolius Raf. in New England. It has submersed leaves 0.2–1.8 mm wide that are 3 (–5)-veined, with or without a narrow 
band of lacunae bordering the midrib. The stipules are 3–34 mm long, mostly distinct from the leaf but some connate for a short distance (up to 2.8 mm). The floating leaves, which are always present on flowering plants, are 18–35 ×5–11 mm and have 9–15 
veins. The hybrid shows dimorphic inflorescences (within a population), with some short ones (2–3 mm) in the axils of submerged leaves and longer ones (3–6 mm) in emersed spikes. This hybrid is known from CT, MA, and is found primarily in slow-moving, circumneutral water of rivers.

7×19. Potamogeton epihydrus × Potamogeton perfoliatus → Potamogeton ×‌versicolor Z. Kaplan, Hellquist, & Fehrer is a rare pondweed known from ME. It ± resembles Potamogeton alpinus, but the submersed blades have prominent lacunar bands, and the narrow-lanceolate blades sometimes have weakly clasping bases. Floating leaves are sometimes produced on mature plants and have short petioles 4–22 mm long (compared with 20–125 mm in P. epihydrus). This hybrid closely resembles P. ×‌nitens ( P. gramineus ×P. perfoliatus) but has submersed leaves 4–11 mm wide and floating leaves 22–32 mm long with apically winged petioles 4–22 mm long (vs. submersed leaves 5–23 mm and floating leaves 27–65 mm with apically unwinged or barely winged petioles 12–40 mm long).