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Potamogeton vaseyi — Vasey's pondweed

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Facts

Vasey's pondweed is a regionally rare plant in New England that can be difficult to separate from small pondweed (Potamogeton pusillus) when floating leaves are absent.

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
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • 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
  • whorled: there are three or more leaves per node along the stem
Leaf blade length
20–80 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
  • the leaf blade is elliptic (widest near the middle and tapering at both ends)
  • the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
Underwater leaf blade width
0.1–1 mm
Fruit type (general)
  • the fruit is dry but does not split open when ripe
  • the fruit is fleshy
Underwater leaf length
20–80 mm
Show all characteristics

  • Clonal plantlets

    Turion length
    5–20 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
    2–6
    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
    6–8 mm
    Inflorescence type
    the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
    Length of peduncle
    5–30 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
    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
    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
    0.3–0.5 mm
    Fruit length
    1.5–2.5 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
    1.2–1.6 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
    the plant has turions
    Underground organs
    there are only slender roots on the plant

  • 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
    3–8 mm
    Floating leaf length
    6–15 mm
    Floating leaf shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    Floating leaf tip
    the tip of the floating leaf blade is obtuse (bluntly pointed)
    Floral bract form
    NA
    Floral bract length
    0 mm
    Leaf arrangement
    • alternate: there is one leaf per node along the stem
    • whorled: there are three or more leaves per node along the stem
    Leaf blade length
    20–80 mm
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf blade width
    0.1–1 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 do not forma 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 capillary (very fine and hair-like)
    • the underwater leaf blade is linear (very narrow with more or less parallel sides)
    Underwater leaf blade veins
    1–3
    Underwater leaf blade width
    0.1–1 mm
    Underwater leaf length
    20–80 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 caudate (has a very long tail-like projection ending in a point)
    Veins in floating leaf
    5–9

  • Place

    Habitat
    aquatic
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • 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)

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), threatened (code: T)
Maine
rare (S-rank: S2), special concern (code: SC)
Massachusetts
extremely rare (S-rank: S1), endangered (code: E)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)
Vermont
rare (S-rank: S2)

From Flora Novae Angliae dichotomous key

27.  Potamogeton vaseyi J.W. Robbins NC

Vasey’s pondweed. Potamogeton lateralis Morong, pro parte • CT, MA, ME, NH, VT. Shallow, still or slow-moving, circumneutral water of lakes and rivers. Potamogeton lateralis was believed to be an extremely rare taxon that occurred in New England. However, the original material (including the lectotype) was a mixture of P. pusillus and P. vaseyi. Potamogeton vaseyi senesces early, and the stems are typically gone by mid-August. It is very difficult to separate from P. pusillus when floating leaves are absent; however, P. vaseyi lacks nodal glands, often has narrower submersed blades, lacks lacunar bands on submersed leaves, and has turions on short, divergent, axillary branches ( P. pusillus has nodal glands on at least some nodes, often has wider leaf blades (see identification key), sometimes has 1 or 2 more rows of lacunae on submersed leaves, and has turions on elongate, ascending, terminal branches).

Native to North America?

Yes

Sometimes confused with

Potamogeton gemmiparus:
floating leaves not produced and nodal glands present on at least some nodes (vs. P. vaseyi, with floating leaves often produced on some plants in a population and nodal glands absent).

Synonyms

  • Potamogeton lateralis Morong, pro parte

Family

Potamogetonaceae

Genus

Potamogeton