Glyceria maxima (Hartman) Holmb.

reed 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

Reed manna grass is native to northern Eurasia. It is considered a noxious weed in much of its introduced range due to its ability to form huge monospecific stands in wetlands. In New England it has been collected from wet, disturbed sites in Connecticut and Massachusetts. It was introduced to North America some time before 1940, and is a recent arrival in New England, having been first collected in New England on the Ipswich River in Essex County, Massachusetts in 1990.

Habitat

Anthropogenic (man-made or disturbed habitats), riverine (in rivers or streams), shores of rivers or lakes

Characteristics

Habitat
  • aquatic
  • wetlands
New England state
  • Connecticut
  • Massachusetts
Leaf blade width
6–20 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
5–12 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
Leaf ligule length
1.2–6 mm
Anther length
1–2 mm
Show All Characteristics
  • Flowers
    Anther length
    1–2 mm
    Anther number
    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
    4–10
    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 hairs
    the inflorescence axis is rough and feels like sand-paper
    Inflorescence axis orientation
    • the inflorescence axis is arched or curved outward
    • the inflorescence axis is straight
    Inflorescence branch length
    8–20 cm
    Inflorescence branch roughness
    the inflorescence branches are somewhat to very rough
    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
    4–10
    Inflorescence crowding
    the panicle is somewhat to very spread out, with clearly-evident branches
    Inflorescence length
    150–450 mm
    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
    Up to 300 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 marginal vein hairs
    the marginal vein of the lemma is hairless
    Lemma surface
    the surface of the lemma is relatively smooth (not counting any longitudinal veins or hairs)
    Lemma tip
    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 is rounded off or truncate (ends abruptly in a more or less straight line as though cut off); it may or may not also have an awn or teeth at the tip
    • the lemma tip tapers to a broad point (it may or may not also have an awn or teeth at the tip)
    • 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
    2–3 mm
    One or more florets
    there is more than one floret per spikelet
    Palea length
    3–4 mm
    Palea relative length
    palea is one half to fully as long as lemma
    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
    5–12 mm
    Spikelet number per node
    0
    Spikelet pedicel
    the spikelets have pedicels
    Spikelet pedicel length
    0.8–10 mm
    Spikelet position
    the spikelets emerge mainly from the upper halves of the inflorescence branches
    Spikelet shape
    the spikelets are ovate (egg-shaped, widest below the middle with rounded ends) in profile
    Spikelet width
    2–3.5 mm
    Spikelets per panicle branch
    At least 50
    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
    2.5–4 mm
    Upper glume shape
    the upper glume is widest at or below the middle
  • Fruits or seeds
    Seed length
    1.5–2 mm
  • Growth form
    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 basal lobe hairy
    NA
    Leaf blade base
    the leaf is tapered gradually to the base
    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
    30–60 cm
    Leaf blade texture
    • the leaf blade is rough and sandpapery
    • the leaf blade is smooth, or it may have soft hairs
    Leaf blade width
    6–20 mm
    Leaf ligule length
    1.2–6 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 upright, or at less than a 45 degree angle out from the stem
  • Place
    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Massachusetts
    Specific habitat
    • in rivers or streams
    • man-made or disturbed habitats
    • shores of rivers or lakes
  • Stem, shoot, branch
    Hairs at nodes
    the stem nodes are hairless or they have very sparse hairs
    Plant height
    60–250 cm
    Stem hairs
    the stem is nearly to completely hairless
    Stem orientation
    the stems are upright
    Stem spacing
    the stems grow singly or a few together (they may form diffuse colonies)
    Stem thickness at base
    6–12 mm

Wetland Status

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

New England Distribution and Conservation Status

Distribution

Connecticut
present, invasive, prohibited
Maine
absent
Massachusetts
present, invasive, prohibited
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
unranked (S-rank: SNR)

Native to North America?

No

Sometimes Confused With

Glyceria grandis

Synonyms

  • Glyceria spectabilis Mert. & Koch
  • Molinia maxima Hartman

Family

Poaceae

Genus

Glyceria

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Information from Dichotomous Key of Flora Novae Angliae

7.  Glyceria maxima (Hartman) Holmb. E

reed manna grass. Glyceria spectabilis Mert. & Koch; Molinia maxima Hartman • CT, MA. Ditches and other wet, disturbed places, muddy stream shores.