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Sagittaria filiformis — narrow-leaved arrowhead

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Facts

Narrow-leaved arrowhead is found in slow to moderately-moving water of rivers, and its morphology can be quite plastic depending on water depth. Only tall plants growing in deep water produce flowers and fruits.

Habitat

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
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • Rhode Island
Leaf position
  • some of the leaves are floating at the surface of the water
  • the leaves are all submerged underwater
Leaf arrangement
basal: the leaves are growing only at the base of the plant
Leaf blade length
300–2500 mm
Petal or sepal number
there are three petals, sepals, or tepals in the flower
Petal color
white
Specific leaf type
the leaf is not divided, rather the blade is made up of one segment
Floating leaf shape
  • the leaf blade is linear (very narrow with more or less parallel sides)
  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
  • the leaf blade is sagittate (arrow-shaped with backward-facing pointed lobes)
Underwater leaf blade width
1–15 mm
Fruit type (general)
the fruit is dry but does not split open when ripe
Underwater leaf length
300–2500 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
    • the flowers are below the surface of the water
    • the flowers are floating on 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
    150–250 mm
    Inflorescence type
    the inflorescence is a raceme (a long unbranched stem with stalked flowers growing along it)
    Inflorescence width
    50–150 mm
    Length of flower stalk
    15–45 mm
    Length of peduncle
    100–2000 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    At least 3
    Ovary position
    the sepals and/or petals are attached below the ovary
    Palate on corolla
    no
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal color
    white
    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 number
    3
    Petal or sepal number
    there are three petals, sepals, or tepals in the flower
    Pistil number
    6 or more
    Sepal appearance
    the sepals resemble leaves in color and texture
    Sepal number
    3
    Spur length
    0 mm
    Stamen number
    • 10
    • 11
    • 12
    • 13 or more
    • 7
    • 8
    • 9
    Stamen position relative to petals
    NA
    Stamens fused to petals
    the stamens are not fused to the petals or tepals

  • Fruits or seeds

    Fruit beak length
    1 mm
    Fruit length
    5 mm
    Fruit type (general)
    the fruit is dry but does not split open when ripe
    Fruit type (specific)
    the fruit is an achene (dry, usually 1-seeded, does not separate or split open at maturity)
    Fruit width
    2.5 mm

  • Glands or sap

    Sap
    the sap is milky and opaque, and may be white or colored

  • Growth form

    Lifespan
    the plant lives more than two years
    Root septa
    the roots 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 one or more swollen storage organs underground, such as bulbs, tubers or corms

  • Leaves

    Bract position (Sparganium)
    NA
    Bract relative length
    At least 1379 mm
    Bracts
    the flowers or their pedicels have bracts at their bases
    Floating leaf basal lobes
    no
    Floating leaf blade width
    Up to 5 mm
    Floating leaf length
    Up to 400 mm
    Floating leaf shape
    • the leaf blade is linear (very narrow with more or less parallel sides)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    • the leaf blade is sagittate (arrow-shaped with backward-facing pointed lobes)
    Floating leaf tip
    • the tip of the floating leaf blade is acute (sharply pointed)
    • 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
    Up to 110 mm
    Leaf arrangement
    basal: the leaves are growing only at the base of the plant
    Leaf blade length
    300–2500 mm
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf blade width
    1–15 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
    the leaf-like branches are flat
    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 linear (very narrow with more or less parallel sides)
    Underwater leaf blade width
    1–15 mm
    Underwater leaf length
    300–2500 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 rounded, with no point
    Veins in floating leaf
    anything

  • Place

    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • Rhode Island
    Specific habitat
    in rivers or streams

  • Stem, shoot, branch

    Flowering stem growth form
    • the flowering stem is upright
    • 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
present
Maine
present
Massachusetts
present
New Hampshire
absent
Rhode Island
present
Vermont
absent

Conservation status

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

Maine
rare (S-rank: S2), special concern (code: SC)
Massachusetts
fairly widespread (S-rank: S4)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)

From Flora Novae Angliae dichotomous key

3.  Sagittaria filiformis J.G. Sm. N

narrow-leaved arrowhead. Sagittaria stagnorum Small; S. subulata (L.) Buch. var. gracillima (S. Wats.) J.G. Sm. • CT, MA, ME, RI. Slow to moderately moving rivers, including fresh-tidal sections. Sagittaria filiformis is, like many arrowheads, a very plastic species. Field and museum observations suggest that some characters used to distinguish S. filiformis from S. subulata are not reliable. Though most collections of these two taxa are markedly different, it is likely the result of sampling in widely spaced locations. Specimens taken from some tidal rivers, where exposed shoreline and deep-water habitats co-occur, show a morphological cline between short plants with emergent leaves and tall plants with long, flaccid leaves (though only the tall plants in deep water produce flowers and fruits). It is apparent that determinations based on vegetative, short-leaved plants may be inaccurate (though long-leaved plants are certainly S. filiformis). Adams and Godfrey (1961) have discussed morphological confluence of species within this complex in the southeastern United States.

Native to North America?

Yes

Sometimes confused with

Sagittaria subulata:
leaves of reproductive plants 5–30 cm long, peduncles 5–40 cm long, and plants predominantly of brackish, tidal shores (vs. S. filiformis, with leaves of reproductive plants mostly 30–90 cm long, peduncles 10–200 cm long, and plants predominantly of fresh, moderately moving rivers).

Synonyms

  • Sagittaria stagnorum Small
  • Sagittaria subulata (L.) Buch. var. gracillima (S. Wats.) J.G. Sm.

Family

Alismataceae

Genus

Sagittaria