Elymus riparius Wieg.

eastern riverbank wild-rye

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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

Eastern riverbank wild-rye grows in the alluvial soils in woods and thickets (riparian zone) along larger streams. It occasionally forms hybrids with other wild-rye (Elymus) species.

Habitat

Forests, shores of rivers or lakes

Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf blade width
5–25 mm
Inflorescence branches
there are no branch points between the base of the inflorescence axis and the flowers, or they are not obvious
Spikelet length
10–20 mm
Glume relative length
  • both glumes are as long or longer than all of the florets
  • neither glume is quite as long as all of the florets
Awn on glume
the glume has an awn
One or more florets
there is more than one floret per spikelet
Lemma awn length
15–35 mm
Leaf sheath hair type
there are no hairs on the surface of the leaf sheath
Leaf ligule length
Up to 1 mm
Anther length
2–2.7 mm
Show All Characteristics
  • Flowers
    Anther length
    2–2.7 mm
    Anther number
    3
    Awn on glume
    the glume has an awn
    Bristles below spikelets
    no
    Floret lower bract texture
    the lemma is thin and flexible
    Floret number
    2–4
    Floret types within spikelet
    all the florets within a spikelet are similar
    Glume awn length
    0–18 mm
    Glume keel
    NA
    Glume relative length
    • both glumes are as long or longer than all of the florets
    • neither glume is quite as long as all of the florets
    Glume shape
    the glume is flat or curved in cross-section
    Glume veins
    3
    Glumes per spikelet
    2
    Inflorescence arrangement
    the spikelets are uniform
    Inflorescence axis hairs
    • the inflorescence axis is rough and feels like sand-paper
    • the inflorescence axis is smooth and has no hairs
    Inflorescence axis orientation
    • the inflorescence axis bends downwards or hangs
    • the inflorescence axis is arched or curved outward
    Inflorescence branch length
    0 cm
    Inflorescence branch roughness
    NA
    Inflorescence branches
    there are no branch points between the base of the inflorescence axis and the flowers, or they are not obvious
    Inflorescence branches coming off the lowest stem node
    0
    Inflorescence crowding
    NA
    Inflorescence length
    70–250 mm
    Inflorescence length to width ratio
    3.5–6.3
    Inflorescence type (general)
    the inflorescence is a spike, or is spike-like, lacking obvious branches
    Inflorescence type (specific)
    the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
    Inflorescence width
    20–40 mm
    Inforescence position
    the spikelets are mainly carried at the end of the stem
    Lemma awn base
    the awn is attached right at the tip of the lemma
    Lemma awn coiled
    • the lemma awn is coiled at least one half turn
    • the lemma awn is straight or twisted, but not coiled one half turn
    Lemma awn length
    15–35 mm
    Lemma awn number
    the lemma has one awn on it
    Lemma awn orientation
    • the awn of the lemma is straight
    • the awn of the lemma on dried or older plants is curved or bent outwards
    Lemma cross-section
    the lemma is flat or rounded if you cut across the midpoint
    Lemma hairs
    • the lemma has fine hairs between the veins
    • the lemma is hairless between the veins
    Lemma keel hairs
    NA
    Lemma marginal vein hairs
    • the marginal vein of the lemma has fine hairs on it
    • 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 tapers to a narrow point (it may or may not also have an awn or teeth at the tip)
    Lemma vein number
    5
    Lemma vein orientation
    the veins on the lemma stay roughly parallel throughout
    Lower glume length
    9–17 mm
    Lower glume relative length
    the lower glume is nearly as long, or as long as, the upper glume
    One or more florets
    there is more than one floret per spikelet
    Palea length
    6–9 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
    10–20 mm
    Spikelet number per node
    2–3
    Spikelet pedicel
    the spikelets do not have pedicels
    Spikelet pedicel length
    0 mm
    Spikelet position
    NA
    Spikelet shape
    • the spikelets are elliptic (widest in the middle, tapering to the ends) in profile
    • the spikelets are oblong (rectangular, but with rounded ends) in profile
    Spikelets per panicle branch
    0
    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
    9–17 mm
    Upper glume relative length
    the upper glume is more than one half as long as the lowest lemma
  • Fruits or seeds
    Groove on seed
    the caryopsis has a groove running most of its length
  • Growth form
    Horizontal rooting stem
    no
    Lifespan
    the plant lives more than two years
    Rhizomes
    no
    Roots
    there are only slender roots on the plant
  • Leaves
    Basal leaves
    the plant has few or no leaves coming from the base of the flowering stem
    Leaf auricles
    • the leaves do not have auricles
    • the leaves 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 texture
    the leaf blade is rough and sandpapery
    Leaf blade width
    5–25 mm
    Leaf ligule length
    Up to 1 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 overlapping and not fused together except in the basal half (or less)
    Leaf sheath color and persistence
    the leaf sheathes are reddish-brown and disintegrate or become shredded in older leaves
    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
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • forests
    • shores of rivers or lakes
  • Stem, shoot, branch
    Hairs at nodes
    the stem nodes are hairless or they have very sparse hairs
    Plant height
    70–160 cm
    Roots at lower stem nodes
    • no
    • yes
    Stem hairs
    the stem is nearly to completely hairless
    Stem node number
    5–10
    Stem orientation
    the stems are upright
    Stem spacing
    the stems grow close together in compact clusters or tufts

Wetland Status

Usually occurs in wetlands, but occasionally in non-wetlands. (Wetland indicator code: FACW)

New England Distribution and Conservation Status

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)

Native to North America?

Yes

Sometimes Confused With

Elymus villosus:
leaf blades softly pubescent on the adaxial surface, internodes of spike mostly 2-3 mm long, and lemmas usually villous (vs. E. riparius, with leaf blades glabrous or scabrous on the adaxial surface, internodes of spike mostly 3-5 mm long, and lemmas usually minutely scabrous).

Synonyms

  • Elymus canadensis var. riparius (Wieg.) Boivin

Family

Poaceae

Genus

Elymus

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Information from Dichotomous Key of Flora Novae Angliae

7.  Elymus riparius Wieg. N

eastern riverbank wild-rye. Elymus canadensis L.  var. riparius (Wieg.) Boivin • CT, MA, ME, NH, 
 RI, VT. Riparian forests, river banks.

4×7. Elymus hystrix × Elymus riparius This very rare wild-rye hybrid is known from VT. It generally resembles Elymus riparius with a large, arching spike. However, the spike internodes are 6–7 mm long (rather than 3–5 mm long), the glumes range in development from nearly absent or merely slender bristles (as in E. hystrix) to fully developed (as in E. riparius), and the spikelets are more loosely spreading than in typical E. riparius.

7×11. Elymus riparius × Elymus wiegandii This very rare wild-rye hybrid is known from VT. It is largely sterile (as shown by its abortive pollen) and on the surface appears to be a less robust, narrower-leaved form of Elymus wiegandii (i.e., it often has the conspicuously drooping spikes of that species). However, the hybrid plants show spikelets with mostly 2 or 3 florets, indurate and usually unstriate glume bases, and paleas mostly 10–10.5 mm long (with nodding or arching spikes, spikelets with mostly 2 florets, indurate and unstriate glume bases, and paleas 6–9 mm long in E. riparius vs. conspicuously drooping spikes, spikelets with mostly 4–6 florets, slightly indurate and somewhat striate glume bases, and paleas 9–14 mm long in E. wiegandii).