Aristida tuberculosa Nutt.

seaside threeawn

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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

Seaside threeawn is a plant of coastal sand dunes in New England. It has notably unusual awns that are loosely twisted around one another at the base. This is a great illustration of functional morphology, as the awns remain attached to the caryopsis (fruit) after dispersal, and function to bury the caryopsis in the sand as the awns twist and untwist with changes in humidity.

Habitat

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

Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Massachusetts
  • New Hampshire
Leaf blade width
2–4 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
6–12 mm
Glume relative length
both glumes are as long or longer than all of the florets
Awn on glume
the glume has an awn
One or more florets
there is one floret per spikelet
Lemma awn length
38–55 mm
Leaf sheath hair type
  • there are hairs on the surface of the leaf sheath, but the hairs do not have blisters at their bases
  • there are no hairs on the surface of the leaf sheath
Show All Characteristics
  • Flowers
    Anther number
    3
    Awn on glume
    the glume has an awn
    Bristles below spikelets
    no
    Floret lower bract texture
    the lemma is hard and firm
    Floret number
    1
    Floret types within spikelet
    all the florets within a spikelet are similar
    Glume awn length
    5–10 mm
    Glume relative length
    both glumes are as long or longer than all of the florets
    Glume veins
    1
    Glumes per spikelet
    2
    Inflorescence arrangement
    the spikelets are uniform
    Inflorescence axis orientation
    the inflorescence axis is straight
    Inflorescence branch length
    1–4 cm
    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 congested (crowded), and the branches may not be clearly seen without close inspection
    • the panicle is somewhat to very spread out, with clearly-evident branches
    Inflorescence length
    100–200 mm
    Inflorescence length to width ratio
    2–3.3
    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
    30–100 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
    Lemma awn length
    38–55 mm
    Lemma awn number
    the lemma has more than one awn on it
    Lemma awn orientation
    the awn of the lemma on dried or older plants is curved or bent outwards
    Lemma base hairs
    the lemma has hairs at the base
    Lemma base length
    3–4 mm
    Lemma cross-section
    the lemma is flat or rounded 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 a simple point, with or without an awn (long narrow extension ending in a point)
    Lemma vein number
    3
    Lower glume length
    20–30 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 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 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
    6–12 mm
    Spikelet number per node
    0
    Spikelets per panicle branch
    1–4
    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
    20–30 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
    8–10 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 hairs
    the leaf blade is hairless, but it may have tiny prickles that give it a sand-papery feel
    Leaf blade length
    8–25 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
    2–4 mm
    Leaf ligule type
    the leaf ligule is in the form of fine hairs
    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 hair type
    • there are hairs on the surface of the leaf sheath, but the hairs do not have blisters at their bases
    • there are no hairs on the surface of the leaf sheath
    Leaf sheath hairs
    • there are hairs on the surface of the leaf sheath
    • there are no hairs on the surface of the leaf sheath
  • Place
    Habitat
    terrestrial
    New England state
    • Connecticut
    • Massachusetts
    • New Hampshire
    Specific habitat
    • dunes
    • grasslands
    • man-made or disturbed habitats
    • meadows or fields
  • Stem, shoot, branch
    Hairs at nodes
    the stem nodes are hairless or they have very sparse hairs
    Plant height
    25–100 cm
    Stem hairs
    the stem is nearly to completely hairless
    Stem orientation
    • the stems are upright
    • the stems trail at the base, but turn upwards at the tips
    Stem spacing
    the stems grow close together in compact clusters or tufts

Wetland Status

Not classified

New England Distribution and Conservation Status

Distribution

Connecticut
present
Maine
absent
Massachusetts
present
New Hampshire
present
Rhode Island
absent
Vermont
absent

Conservation Status

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

Connecticut
extremely rare (S-rank: S1), endangered (code: E)
Massachusetts
rare (S-rank: S2), threatened (code: T)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)

Native to North America?

Yes

Sometimes Confused With

Aristida oligantha:
lemma awns not twisted together at the base and callus of lemma 0.5-2 mm long (vs. A. tuberculosa, with lemma awns twisted together at the base forming a spiral column 8–15 mm tall and callus of lemma 3–4 mm long).

Family

Poaceae

Genus

Aristida

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Information from Dichotomous Key of Flora Novae Angliae

7.  Aristida tuberculosa Nutt. N

seaside threeawn. CT, MA, NH. Coastal dunes, dry, sterile, sandy soil near the coast.