Glyceria fluitans (L.) R. Br.

water manna grass

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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

Water manna grass is introduced in North America, and has been collected in Massachusetts. This Eurasian species has edible seeds. In a study of the gut contents of Paleolithic and Mesolithic humans preserved in bogs in Poland, water manna grass seeds were among six plant species that were commonly collected for food in that region in prehistoric times.

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams), shores of rivers or lakes, wetland margins (edges of wetlands)

Characteristics

Habitat
  • aquatic
  • wetlands
New England state
Massachusetts
Leaf blade width
3–10 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
15–39 mm
Glume relative length
neither glume is quite as long as all of the florets
Awn on glume
the glume has no awn
One or more florets
there is more than one floret per spikelet
Lemma awn length
0 mm
Leaf sheath hair type
there are no hairs on the surface of the leaf sheath
Anther length
1.5–3 mm
Show All Characteristics
  • Flowers
    Anther length
    1.5–3 mm
    Anther number
    2–3
    Awn on glume
    the glume has no awn
    Bristles below spikelets
    no
    Floret lower bract texture
    the lemma is thin and flexible
    Floret number
    8–16
    Floret types within spikelet
    all the florets within a spikelet are similar
    Glume awn length
    0 mm
    Glume relative length
    neither glume is quite as long as all of the florets
    Glume veins
    1
    Glumes per spikelet
    2
    Inflorescence arrangement
    the spikelets are uniform
    Inflorescence axis orientation
    • the inflorescence axis is arched or curved outward
    • the inflorescence axis is straight
    Inflorescence branch length
    3–17 cm
    Inflorescence branches
    the flowers are attached to branches rather than to the main axis of the inflorescence
    Inflorescence branches coming off the lowest stem node
    1–2
    Inflorescence crowding
    the panicle is somewhat to very spread out, with clearly-evident branches
    Inflorescence length
    100–500 mm
    Inflorescence length to width ratio
    5–16.7
    Inflorescence type (general)
    the spikelets are borne on stalks or on branches
    Inflorescence type (specific)
    the inflorescence is branched, and the branches do NOT both grow from the same side of the plant AND look like spikes
    Inflorescence width
    20–30 mm
    Inforescence position
    the spikelets are mainly carried at the end of the stem
    Lemma awn base
    NA
    Lemma awn coiled
    NA
    Lemma awn length
    0 mm
    Lemma awn number
    the lemma has no awn
    Lemma awn orientation
    NA
    Lemma base hair length
    0 mm
    Lemma base hairs
    the lemma is hairless or feels just a tiny bit rough at the base
    Lemma cross-section
    the lemma is flat or rounded if you cut across the midpoint
    Lemma hairs
    the lemma is hairless between the veins
    Lemma keel hairs
    NA
    Lemma surface
    the surface of the lemma is relatively smooth (not counting any longitudinal veins or hairs)
    Lemma tip
    • the lemma tip has a ragged edge
    • the lemma tip is a simple point, with or without an awn (long narrow extension ending in a point)
    Lemma tip shape
    the lemma tip tapers to a narrow point (it may or may not also have an awn or teeth at the tip)
    Lemma vein number
    7 or more
    Lemma vein orientation
    the veins on the lemma stay roughly parallel throughout
    Lower glume length
    1.3–1.9 mm
    One or more florets
    there is more than one floret per spikelet
    Reproductive system
    all the flowers on the plant have both carpels and stamens (synoecious)
    Spikelet axis tip
    there is no extension of the spikelet axis beyond the tip of the spikelet
    Spikelet disintegration
    the spikelet breaks off above the glumes, so that after the florets fall off, the glumes remain
    Spikelet length
    15–39 mm
    Spikelet number per node
    Up to 0
    Spikelet pedicel
    the spikelets have pedicels
    Spikelet pedicel length
    0.8–20 mm
    Spikelet position
    the spikelets emerge from both the upper and lower halves of the inflorescence branches
    Spikelet shape
    the spikelets are another shape in profile
    Spikelet width
    1.7–3.3 mm
    Spikelets per panicle branch
    1–4
    Spikelets spiny
    the spikelets do not appear spiny
    Tip of glume
    the tip of the glume is not divided (though it may have an awn on it)
    Upper glume length
    2.7–5 mm
    Upper glume shape
    the upper glume is widest at or below the middle
  • Fruits or seeds
    Seed length
    2–3 mm
  • Growth form
    Horizontal rooting stem
    no
    Lifespan
    the plant lives more than two years
    Rhizomes
    yes
    Roots
    the plant has rhizomes (horizontal underground stem with roots growing from it)
  • Leaves
    Leaf auricles
    the leaves do not have auricles
    Leaf blade cross-section
    the leaf blade is more or less flat in cross-section, or slightly folded or rolled inwards
    Leaf blade hairs
    the leaf blade is hairless, but it may have tiny prickles that give it a sand-papery feel
    Leaf blade length
    5–25 cm
    Leaf blade texture
    the leaf blade is smooth, or it may have soft hairs
    Leaf blade width
    3–10 mm
    Leaf ligule type
    the leaf ligule is in the form of a membrane
    Leaf margin glands
    there are no glands along the edges of the leaf blade
    Leaf sheath closed around stem
    the margins of the leaf sheath are fused together and form a closed tube except (possibly) at the very top
    Leaf sheath hair type
    there are no hairs on the surface of the leaf sheath
    Leaf sheath hairs
    there are no hairs on the surface of the leaf sheath
    Orientation of topmost leaf
    • the flag leaf is held outward at more than a 45 degree angle from the stem, or it curves downwards from the horizontal
    • the flag leaf is held upright, or at less than a 45 degree angle out from the stem
  • Place
    Habitat
    • aquatic
    • wetlands
    New England state
    Massachusetts
    Specific habitat
    • edges of wetlands
    • in lakes or ponds
    • in rivers or streams
    • shores of rivers or lakes
  • Stem, shoot, branch
    Hairs at nodes
    the stem nodes are hairless or they have very sparse hairs
    Plant height
    20–150 cm
    Roots at lower stem nodes
    • no
    • yes
    Stem hairs
    the stem is nearly to completely hairless
    Stem orientation
    • the stems are upright
    • the stems trail along the ground or on other plants through most or all of their length
    • the stems trail at the base, but turn upwards at the tips
    Stem thickness at base
    2–4 mm

Wetland Status

Occurs only in wetlands. (Wetland indicator code: OBL)

New England Distribution and Conservation Status

Distribution

Connecticut
absent
Maine
absent
Massachusetts
present
New Hampshire
absent
Rhode Island
absent
Vermont
absent

Conservation Status

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

Massachusetts
not applicable (S-rank: SNA)

Native to North America?

No

Sometimes Confused With

Glyceria acutiflora:
spikelets 20-40 mm long, with lemmas 7-8.5 mm long, acute at the apex, and teeth at apex of paleas 0.4-1 mm long (vs. G. fluitans, with lemmas 5.4-7 mm long, truncate to obtuse at the apex, and teeth at apex of paleas 0.1-0.4 mm long).
Glyceria septentrionalis:
lemmas 3.7–5.3 mm long, internodes of rachilla 1.1–1.8 mm long, and anthers 1–1.7 mm (vs. G. fluitans, with lemmas 5.4–7 mm long, internodes of rachilla 1.9–2.5 mm long, and anthers 2–3 mm long).

Synonyms

  • Festuca fluitans L.
  • Panicularia fluitans (L.) Kuntze

Family

Poaceae

Genus

Glyceria

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Information from Dichotomous Key of Flora Novae Angliae

4.  Glyceria fluitans (L.) R. Br. E

water manna grass. Festuca fluitans L.; Panicularia fluitans (L.) Kuntze • MA. Shallow water 
of pools, lakes, and streams.