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
- unranked (S-rank: SNR)
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:
- plants mostly with 5-7 veins and 2-7 roots (vs. S. polyrrhiza, which are plants with mostly 7-16 veins and 7-21 roots).
Synonyms
- Lemna polyrrhiza L.
- Spirodela polyrrhiza (L.) Schleid. var. masonii Daubs