Limnobium spongiosa (Bosc) Rich. ex Steud.

American spongeplant

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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

American spongeplant is native to the southeastern states. It has thick, spongy, floating leaves and thinner emergent leaves that lack the spongy tissue. After fertilization, the peduncle curves down, so that the developing fruit is pushed underwater.

Habitat

Shores of rivers or lakes

Characteristics

Habitat
  • aquatic
  • wetlands
New England state
Connecticut
Leaf position
some of the leaves are floating at the surface of the water
Leaf arrangement
basal: the leaves are growing only at the base of the plant
Leaf blade length
20–80 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 cordate (heart-shaped with backward-facing rounded lobes)
  • the leaf blade is orbicular (roughly circular, as wide as long)
  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
Underwater leaf blade width
0 mm
Fruit type (general)
  • the fruit is dry and splits open when ripe
  • the fruit is fleshy
Underwater leaf length
0 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
    Anther length
    2–4 mm
    Carpels fused
    the carpels are fused to one another
    Flower lower lip length
    0 mm
    Flower number
    1–9
    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
    25–100 mm
    Inflorescence type
    the inflorescence is a monochasial cyme (an axis with a terminal flower, below it a branch with a terminal flower, this branch may itself have a branch and so on)
    Length of flower stalk
    30–100 mm
    Length of peduncle
    25–100 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    6–9
    Ovary position
    the sepals and/or petals are attached above 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 length
    8–10 mm
    Petal number
    3–4
    Petal or sepal number
    there are three petals, sepals, or tepals in the flower
    Pistil number
    1
    Sepal appearance
    the sepals resemble petals in color and texture
    Sepal length
    7–10 mm
    Sepal number
    3
    Sepals fused only to sepals
    the sepals are separate from one another
    Spur length
    0 mm
    Stamen number
    • 10
    • 11
    • 12
    • 13 or more
    • 9
    Stamen position relative to petals
    NA
    Stamens fused
    • the stamens are fused to one another at or near their bases
    • the stamens are not fused to one another
    Stamens fused to petals
    the stamens are not fused to the petals or tepals
    Style number
    3–9
  • Fruits or seeds
    Fruit length
    10–15 mm
    Fruit type (general)
    • the fruit is dry and splits open when ripe
    • the fruit is fleshy
    Fruit type (specific)
    the fruit is a berry (fleshy, with the wall enclosing one or more sections, with two or more seeds)
    Fruit width
    4–12 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
    Turions
    there are no turions on the plant
  • Leaves
    Bract position (Sparganium)
    NA
    Bracts
    the flowers or their pedicels have bracts at their bases
    Floating leaf basal lobes
    yes
    Floating leaf blade width
    20–50 mm
    Floating leaf length
    20–80 mm
    Floating leaf shape
    • the leaf blade is cordate (heart-shaped with backward-facing rounded lobes)
    • the leaf blade is orbicular (roughly circular, as wide as long)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    Floating leaf tip
    • the tip of the floating leaf blade is acuminate (tapers to a long, thin point)
    • the tip of the floating leaf blade is acute (sharply pointed)
    • the tip of the floating leaf blade is obtuse (bluntly pointed)
    Floral bract form
    the bracts are roughly as lobed as the foliage leaves
    Floral bract length
    30–50 mm
    Leaf arrangement
    basal: the leaves are growing only at the base of the plant
    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
    20–50 mm
    Leaf position
    some of the leaves are floating at the surface of the water
    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 fused to leaf
    the stipules are not attached to the leaf blade at all
    Stipules
    the plant has stipules
    Trap-bladder length
    0 mm
    Underwater leaf air passage number
    At least 1440
    Underwater leaf air passage relative width
    At least 1441
    Underwater leaf blade edges
    the underwater leaf has smooth edges, without teeth
    Underwater leaf blade shape
    NA
    Underwater leaf blade veins
    0
    Underwater leaf blade width
    0 mm
    Underwater leaf length
    0 mm
    Underwater leaf stalk
    yes
    Underwater leaf stalk length
    20–250 mm
    Underwater leaf tip shape
    • the tip of the underwater leaf is acuminate (tapers to a long, thin point)
    • the tip of the underwater leaf is acute (sharply pointed)
    • the tip of the underwater leaf is obtuse (bluntly pointed)
    Veins in floating leaf
    5–7
  • Place
    Habitat
    • aquatic
    • wetlands
    New England state
    Connecticut
    Specific habitat
    shores of rivers or lakes
  • 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
absent
Massachusetts
absent
New Hampshire
absent
Rhode Island
absent
Vermont
absent

Conservation Status

None

Native to North America?

Yes and no (some introduced)

Sometimes Confused With

Hydrocharis morsus-ranae:
primary lateral veins of leaves diverging from midvein at an angle of 75-90 degrees and all leaves having aerenchyma tissue confined to each side of the midrib on the abaxial surface (vs. L. spongiosa, with primary lateral veins of leaves diverging from midvein at an angle of 30-80 degrees and floating leaf blades with conspicuous aerenchyma tissue extending nearly the entire width on the abaxial surface).

Synonyms

  • Hydrocharis spongiosa Bosc

Genus

Limnobium

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Information from Dichotomous Key of Flora Novae Angliae

1.  Limnobium spongiosa (Bosc) Rich. ex Steud. E

American spongeplant. Hydrocharis spongiosa Bosc • CT. Pond shores. This species forms two types of leaf blades—floating ones with conspicuous aerenchyma tissue on the abaxial surface and emergent ones lacking the prominent aerenchyma tissue.