Callitriche stagnalis Scop.

pond water-starwort

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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 About

Pond water-starwort, a widespread old-world species, entered North America at seaports in New York, New Jersey and Oregon, and was well-established on the east coast by 1920. It has since spread about 500 miles from these entry points, and enters New England in Connecticut, Massachusetts and Maine. Water starworts (Callitriche) are remarkable for having flowers able to be pollinated by wind when emergent (anemophily), by water when floating at the surface (epihydrophily), as well as when submerged (hypohydrophily).

Habitat

Brackish or salt marshes and flats, lacustrine (in lakes or ponds), riverine (in rivers or streams)

Characteristics

Habitat
aquatic
New England state
  • Connecticut
  • Massachusetts
Leaf position
  • some of the leaves are floating at the surface of the water
  • the leaves are all submerged underwater
Leaf arrangement
opposite: there are two leaves per node along the stem
Leaf blade length
Up to 20 mm
Petal or sepal number
NA
Petal color
NA
Specific leaf type
the leaf is not divided, rather the blade is made up of one segment
Floating leaf shape
the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
Fruit type (general)
the fruit is dry but does not split open when ripe
Show All Characteristics
  • Clonal plantlets
    Turion length
    0 mm
  • Flowers
    Carpels fused
    the carpels are fused to one another
    Flower lower lip length
    0 mm
    Flower number
    1
    Flower position
    the flowers are below the surface of the water
    Flower symmetry
    NA
    Inflorescence type
    • the flowers grow out of the axil (point where a branch or leaf is attached to the main stem)
    • the inflorescence has only one flower on it
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    2
    Ovary position
    the sepals and/or petals are attached below the ovary
    Palate on corolla
    NA
    Petal and sepal arrangement
    the flower includes neither petals nor sepals
    Petal appearance
    NA
    Petal color
    NA
    Petal fringed edges
    NA
    Petal fusion
    NA
    Petal hairs on inner/upper surface
    NA
    Petal length
    0 mm
    Petal number
    0
    Petal or sepal number
    NA
    Pistil number
    1
    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
    Stamen position relative to petals
    NA
    Stamens fused
    NA
    Stamens fused to petals
    • NA
    • the stamens are not fused to the petals or tepals
    Style number
    2
  • Fruits or seeds
    Fruit length
    1.5–2 mm
    Fruit type (general)
    the fruit is dry but does not split open when ripe
    Fruit type (specific)
    the fruit is a schizocarp (when dry it splits into sections, each holding one or more seeds)
    Fruit width
    1.5–2 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
    there are only slender roots on the plant
  • Leaves
    Bract position (Sparganium)
    NA
    Bracts
    the flowers or their pedicels have bracts at their bases
    Floating leaf basal lobes
    no
    Floating leaf blade width
    3–8 mm
    Floating leaf length
    Up to 20 mm
    Floating leaf shape
    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 rounded, with no point
    Floral bract form
    the bracts are roughly as lobed as the foliage leaves
    Floral bract length
    0.5–1.5 mm
    Leaf arrangement
    opposite: there are two leaves per node along the stem
    Leaf blade length
    Up to 20 mm
    Leaf blade veins
    the lateral veins radiate from the base and continue to spread away from the centerline of the leaf, or branch off the central vein at intervals
    Leaf blade width
    3–8 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
    NA
    Stipule fused to leaf
    NA
    Stipules
    there are no stipules on the plant
    Stipules fused around stem
    NA
    Trap-bladder length
    0 mm
    Underwater leaf blade edges
    the underwater leaf has smooth edges, without teeth
    Underwater leaf blade shape
    • the underwater leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • the underwater leaf blade is linear (very narrow with more or less parallel sides)
    • the underwater leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the underwater leaf blade)
    • the underwater leaf blade is spatulate (spoon-shaped; narrow near the base, then suddenly widening to a rounded tip)
    Underwater leaf blade veins
    1–3
    Underwater leaf stalk
    • no
    • yes
    Underwater leaf tip shape
    the tip of the underwater leaf is retuse (blunt or rounded, with a notch at the tip)
    Veins in floating leaf
    5–7
  • Place
    Habitat
    aquatic
    New England state
    • Connecticut
    • Massachusetts
    Specific habitat
    • brackish or salt marshes and flats
    • in lakes or ponds
    • in rivers or streams

Wetland Status

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

New England Distribution and Conservation Status

Distribution

Connecticut
present, invasive, prohibited
Maine
present
Massachusetts
present
New Hampshire
absent
Rhode Island
absent
Vermont
absent

Conservation Status

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

Massachusetts
unranked (S-rank: SNR)

Native to North America?

No

Sometimes Confused With

Callitriche palustris:
fruit 1-1.4 mm long, with a thin wing near the apical portion, and floating leaf blades was wide as 5 mm, with up to 3 (rarely 5) veins (vs. C. stagnalis, with fruit 1.5-2 mm long, with a thin wing that is equally prominent from the base to the apex, and floating leaf blades 3-8 mm long, with 5-7 veins).
Callitriche hermaphroditica:
leaves monomorphic, all with 1 vein, and flowers and fruits without subtending bracts (vs. C. stagnalis, with leaves dimorphic, the floating ones with 5-7 veins by branching of the lateral veins, and flowers and fruits subtended by 2 white or translucent bracts).

Genus

Callitriche

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Information from Dichotomous Key of Flora Novae Angliae

4.  Callitriche stagnalis Scop. E

pond water-starwort. CT, MA, ME. Shallow water of lakes and brackish-tidal rivers. Philbrick 
et al. (1998) have documented the spread of C. stagnalis in the United States.