Spirodela polyrrhiza (L.) Schleid.

common duck-meal

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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

Common duck-meal is distinguished from the other duckweeds and water-meals by having thalli that are red or reddish purple on the underside and have 7-21 roots hanging from them into the water.

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams)

Characteristics

Habitat
aquatic
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Roots
there are two or more roots per thallus
Thallus shape in cross-section
the thallus is somewhat flattened on at least one side in cross-section
Thallus length
2–10 mm
Thallus shape
  • the thallus is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
  • the thallus is orbicular (roughly circular, as wide as long)
Thallus dimensions
1–1.5
Veins on upper surface
5–21
Show All Characteristics
  • Flowers
    Scale surrounding flower
    yes
    Stamen number
    2
  • Fruits or seeds
    Fruit length
    1–1.5 mm
    Seed surface ribbed
    the seed surface has ribs running from end to end
  • Growth form
    Root length
    Up to 30 mm
    Root number
    7–21
    Root sheath winged at base
    NA
    Roots
    there are two or more roots per thallus
    Roots perforating basal scale
    there are one or two roots protruding through the basal scale
    Thallus dimensions
    1–1.5
    Thallus edge
    the edge of the thallus is smooth (without teeth) near the tip
    Thallus length
    2–10 mm
    Thallus shape
    • the thallus is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    • the thallus is orbicular (roughly circular, as wide as long)
    Thallus shape in cross-section
    the thallus is somewhat flattened on at least one side in cross-section
    Thallus stalks
    the thallus does not have a stalk
    Thallus width
    1.3–10 mm
    Thallus with red pigment
    yes
    Turions
    yes
  • Leaves
    Papilla on thallus
    no
    Veins on upper surface
    5–21
  • Place
    Habitat
    aquatic
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • 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
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
present
Vermont
present

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?

Yes

Sometimes Confused With

Landoltia punctata:
thalli with mostly 5–7 veins, 1.5–2 times as long as wide, and roots numbering mostly 2–7, all perforating the small, membranous scale at thallus base (vs. S. polyrhiza, with thalli with mostly 7–16 veins, 1–1.5 times as long as wide, and roots numbering 7–21 per thallus, only 1 or 2 perforating the small, membranous scale at thallus base).

Synonyms

  • Lemna polyrrhiza L.
  • Spirodela polyrrhiza (L.) Schleid. var. masonii Daubs

Family

Araceae

Genus

Spirodela

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Information from Dichotomous Key of Flora Novae Angliae

1.  Spirodela polyrrhiza (L.) Schleid. N

common duck-meal. Lemna polyrrhiza L.; Spirodela polyrrhiza (L.) Schleid. var. masonii 
 Daubs • CT, MA, ME, NH, RI, VT. Slightly acidic to circumneutral, mesotrophic to eutrophic 
waters of lakes, rivers, beaver flowages, and pools.