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• Poaceae
• Poaceae Group 4
• Glyceria
• Glyceria maxima

Glyceria maxima — reed manna grass

Facts

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

• 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

From the dichotomous key of Flora Novae Angliae