Spirodela polyrrhiza — common duck-meal
![Plant form: Spirodela polyrrhiza. ~ By Arthur Haines. ~ Copyright © 2024 Arthur Haines. ~ arthur.d.haines[at]gmail.com](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Araceae/spirodela-polyrrhiza-ha-ahaines-a.jpg)
![Roots: Spirodela polyrrhiza. ~ By Arthur Haines. ~ Copyright © 2024 Arthur Haines. ~ arthur.d.haines[at]gmail.com](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Araceae/spirodela-polyrrhiza-ro-ahaines-b.jpg)
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Facts
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)
New England distribution
Adapted from BONAP data
Native: indigenous.
Non-native: introduced (intentionally or unintentionally); has become naturalized.
County documented: documented to exist in the county by evidence (herbarium specimen, photograph). Also covers those considered historical (not seen in 20 years).
State documented: documented to exist in the state, but not documented to a county within the state. Also covers those considered historical (not seen in 20 years).
Note: when native and non-native populations both exist in a county, only native status is shown on the map.
Found this plant? Take a photo and post a sighting.
enlargeCharacteristics
- 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
-
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)
In New England
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
- widespread (S-rank: S5)
From Flora Novae Angliae dichotomous key
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.
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