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• Apera interrupta

Apera interrupta — dense silky bentgrass

Facts

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.

Habitat

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

Characteristics

• Flowers

  Anther length

  0.3–0.5 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

  1

  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

  2

  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

  6.7–7.5

  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

  5

  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

  0

  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

  no

  Lifespan

  the plant lives only a single year or less

  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

  Leaf basal lobe hairy

  NA

  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

  Habitat

  terrestrial

  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

From the dichotomous key of Flora Novae Angliae