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Apera interrupta — dense silky bentgrass

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New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data



Dense silky bentgrass was introduced to North America around 1900 and subsequently became an important weed of grain crops in the northwestern United States. It is less common in New England than the closely-related loose silky bentgrass (Apera spica-venti), having been found in only in Massachusetts and Maine. Both species germinate in the fall, overwinter as seedlings, and flower in the spring.


Anthropogenic (man-made or disturbed habitats), meadows and fields


New England state
  • Maine
  • Massachusetts
Leaf blade width
1–3 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
2–2.8 mm
Glume relative length
one or both glumes are as long or longer than all of the florets
Awn on glume
the glume has no awn
One or more florets
there is one floret per spikelet
Lemma awn length
4–16 mm
Leaf ligule length
1.5–5 mm
Anther length
0.3–0.5 mm
Show all characteristics
  • Flowers

    Anther length
    0.3–0.5 mm
    Anther number
    Awn on glume
    the glume has no awn
    Bristles below spikelets
    Floret lower bract texture
    the lemma is thin and flexible
    Floret number
    Floret types within spikelet
    all the florets within a spikelet are similar
    Glume awn length
    0 mm
    Glume relative length
    one or both glumes are as long or longer than all of the florets
    Glume veins
    • 1
    • 3
    Glumes per spikelet
    Inflorescence arrangement
    the spikelets are uniform
    Inflorescence axis orientation
    the inflorescence axis is straight
    Inflorescence branches
    the flowers are attached to branches rather than to the main axis of the inflorescence
    Inflorescence crowding
    the panicle is somewhat to very spread out, with clearly-evident branches
    Inflorescence length
    30–200 mm
    Inflorescence length to width ratio
    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
    4–30 mm
    Inforescence position
    the spikelets are mainly carried at the end of the stem
    Lemma awn base
    the awn is attached at the upper half of the lemma
    Lemma awn coiled
    the lemma awn is straight or twisted, but not coiled one half turn
    Lemma awn length
    4–16 mm
    Lemma awn number
    the lemma has one awn on it
    Lemma awn orientation
    the awn of the lemma is straight
    Lemma base hairs
    the lemma has hairs at the base
    Lemma cross-section
    the lemma is V-shaped if you cut across the midpoint
    Lemma surface
    the surface of the lemma is relatively smooth (not counting any longitudinal veins or hairs)
    Lemma tip
    the lemma tip is split into two or more points
    Lemma vein number
    Lower glume length
    1–2.2 mm
    Lower glume relative length
    the lower glume is one third to three quarters as long as the upper glume
    One or more florets
    there is one floret per spikelet
    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 an 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
    2–2.8 mm
    Spikelet number per node
    Spikelet pedicel
    the spikelets have pedicels
    Spikelet pedicel length
    0.5–2 mm
    Spikelet position
    the spikelets emerge from both the upper and lower halves of the inflorescence branches
    Spikelets spiny
    the spikelets do not appear spiny
    Upper glume length
    2–2.8 mm
    Upper glume relative length
    the upper glume is more than one half as long as the lowest lemma
    Upper glume shape
    the upper glume is widest at or below the middle
  • Fruits or seeds

    Seed length
    1–1.5 mm
  • Growth form

    Horizontal rooting stem
    the plant lives only a single year or less
    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
    Leaf basal lobe hairy
    Leaf blade cross-section
    the leaf blade is more or less flat in cross-section, or slightly folded or rolled inwards
    Leaf blade length
    4–12 cm
    Leaf blade width
    1–3 mm
    Leaf ligule length
    1.5–5 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
  • Place

    New England state
    • Maine
    • Massachusetts
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields
  • Stem, shoot, branch

    Plant height
    5–75 cm
    Stem hairs
    the stem is nearly to completely hairless
    Stem spacing
    • the stems grow close together in compact clusters or tufts
    • the stems grow singly or a few together (they may form diffuse colonies)

Wetland status

Not classified

New England distribution and conservation status


New Hampshire
Rhode Island

Conservation status

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

not applicable (S-rank: SNA)

Native to North America?


Sometimes confused with

Agrostis elliottiana:
panicles open and flowers lacking or with minute paleas and with 1 anther 0.1-0.2 mm long (vs. A. interrupta, with panicle contracted and flowers with well developed paleas 3/4 to fully as long as the associated lemma and with 3 anthers 0.3-0.5 mm long).
Apera spica-venti:
leaf blades mostly 2-5 mm wide, panicles relatively open and 20-150 mm wide, and anthers 1-2 mm long (vs. A. interrupa, with leaf blades mostly 1-3 mm wide, panicles contracted and 4-30 mm wide, and anthers 0.3-0.5 mm long).


  • Agrostis interrupta L.





From the dichotomous key of Flora Novae Angliae

1.  Apera interrupta (L.) Beauv. E

dense silky bentgrass. Agrostis interrupta L. • MA, ME. Lawns, roadsides, fields.