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Native Plant Trust: Go Botany Discover thousands of New England plants

Egeria densa — Brazilian-waterweed

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Facts

Brazilian-waterweed, probably one of the most widely-cultivated aquarium plants, has for this reason become a widespread invasive species of lakes and rivers. Its presence can have pronounced effects on the community composition of aquatic plants where it occurs.

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
  • Massachusetts
  • New Hampshire
  • Vermont
Leaf position
the leaves are all submerged underwater
Leaf arrangement
whorled: there are three or more leaves per node along the stem
Leaf blade length
10–40 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
NA
Underwater leaf blade width
1.5–4.5 mm
Fruit type (general)
the fruit is fleshy
Underwater leaf length
10–40 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 carpels are fused to one another
    Flower lower lip length
    0 mm
    Flower number
    1–4
    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 type
    • the inflorescence has only one flower on it
    • 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
    30–80 mm
    Length of peduncle
    0 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    0–1
    Ovary position
    • NA
    • 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
    9–11 mm
    Petal number
    3
    Petal or sepal number
    there are three petals, sepals, or tepals in the flower
    Pistil number
    • 0
    • 1
    Sepal appearance
    the sepals resemble leaves in color and texture
    Sepal length
    3–4 mm
    Sepal number
    3
    Sepals fused only to sepals
    the sepals are separate from one another
    Spur length
    0 mm
    Stamen number
    9
    Stamen position relative to petals
    NA
    Stamens fused
    the stamens are not fused to one another
    Stamens fused to petals
    the stamens are not fused to the petals or tepals
    Style number
    0–3

  • Fruits or seeds

    Fruit type (general)
    the fruit is fleshy
    Fruit type (specific)
    the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release two or more seeds)

  • 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
    Bract relative length
    At least 1379 mm
    Bracts
    the flowers or their pedicels have bracts at their bases
    Floating leaf basal lobes
    NA
    Floating leaf blade width
    0 mm
    Floating leaf length
    0 mm
    Floating leaf shape
    NA
    Floating leaf tip
    NA
    Floral bract form
    the bracts are roughly as lobed as the foliage leaves
    Floral bract length
    7.5–12 mm
    Leaf arrangement
    whorled: there are three or more leaves per node along the stem
    Leaf blade length
    10–40 mm
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf blade width
    1.5–4.5 mm
    Leaf position
    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
    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 blade edges are toothed
    Underwater leaf blade shape
    the underwater leaf blade is linear (very narrow with more or less parallel sides)
    Underwater leaf blade width
    1.5–4.5 mm
    Underwater leaf length
    10–40 mm
    Underwater leaf stalk
    no
    Underwater leaf stalk length
    0 mm
    Underwater leaf tip shape
    the tip of the underwater leaf is obtuse (bluntly pointed)
    Veins in floating leaf
    0

  • Place

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

  • Stem, shoot, branch

    Flowering stem growth form
    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, invasive, prohibited
Maine
absent
Massachusetts
present, invasive, prohibited
New Hampshire
present, invasive, prohibited
Rhode Island
absent
Vermont
present, invasive, prohibited

Conservation status

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

Massachusetts
not applicable (S-rank: SNA)

From Flora Novae Angliae dichotomous key

1.  Egeria densa Planch. E

Brazilian-waterweed. Anacharis densa (Planch.) Victorin • CT, MA, NH, VT. Shallow, still or slow-moving water of lakes and rivers. This species has been introduced into the United States through the aquarium trade. Only staminate plants are known outside its native range. Vegetative reproduction is likely through plant fragmentation given that no specialized structures for this form of reproduction (e.g., turions, bulbils) have been observed.

Native to North America?

No

Sometimes confused with

Hydrilla verticillata:
leaf blades mostly 8-15 mm long, with small prickles along the abaxial midvein (vs. E. densa, with leaf blades 10-40 mm long, without pickles).
Hippuris vulgaris:
stems upright, emersed from the water, and flowers sessile in the axils of leaves (vs. E. densa, with stems submersed and flowers pedicellate and projected to the surface of the water by an elongate floral tube).

Synonyms

  • Anacharis densa (Planch.) Victorin

Family

Hydrocharitaceae

Genus

Egeria