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• Aristida purpurascens

Aristida purpurascens — arrow-feather threeawn

Facts

Arrow-feather threeawn is a rare plant of New England coastal sandplains, being found in Connecticut, Massachusetts and Rhode Island. This is one of a number of rare plants that colonize disturbed areas within coastal sandplain habitat, such as fire lanes and trails. These species are vulnerable to both development and natural succession, which begs the question, what type of habitat existed historically that could have supported these species? The answer may lie in natural widlfire cycles that maintained successional mosaics in fire-prone habitats before modern fire suppression.

Habitat

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

Characteristics

• Flowers

  Anther length

  1–1.5 mm

  Anther number

  1–3

  Awn on glume

  • the glume has an awn
  • the glume has no 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

  Up to 1 mm

  Glume keel

  • the glume keels are rough or hairy
  • the glume keels are smooth and hairless

  Glume relative length

  both glumes are as long or longer than all of the florets

  Glume shape

  the glume is V-shaped in cross-section

  Glume veins

  1

  Glumes per spikelet

  2

  Inflorescence arrangement

  the spikelets are uniform

  Inflorescence axis orientation

  the inflorescence axis is straight

  Inflorescence branch length

  1–5 cm

  Inflorescence branches

  • the flowers are attached to branches rather than to the main axis of the inflorescence
  • there are no branch points between the base of the inflorescence axis and the flowers, or they are not obvious

  Inflorescence length

  150–550 mm

  Inflorescence length to width ratio

  18.3–30

  Inflorescence type (general)

  • the inflorescence is a spike, or is spike-like, lacking obvious branches
  • the spikelets are borne on stalks or on branches

  Inflorescence type (specific)

  • the inflorescence is a raceme (a long unbranched stem with stalked flowers growing along it)
  • the inflorescence is branched, and the branches do NOT both grow from the same side of the plant AND look like spikes

  Inflorescence width

  5–30 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

  8–25 mm

  Lemma awn number

  the lemma has more than 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 base hairs

  the lemma has hairs at the base

  Lemma base length

  0.4–0.8 mm

  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

  the keel of the lemma is hairless

  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 vein number

  3

  Lower glume length

  5–10 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

  7–10 mm

  Spikelets per panicle branch

  1–8

  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

  5–10 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

  3–5 mm

• Growth form

  Horizontal rooting stem

  no

  Lifespan

  the plant lives more than two years

  Rhizomes

  no

• 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

  10–25 cm

  Leaf blade width

  1–3 mm

  Leaf ligule length

  0.2–0.3 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 color and persistence

  the leaf sheathes are off-white to light-brown and mostly persist in older leaves

  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
  • Rhode Island

  Specific habitat

  • grasslands
  • man-made or disturbed habitats
  • meadows or fields
  • woodlands

• Stem, shoot, branch

  Plant height

  40–100 cm

  Stem orientation

  the stems are upright

  Stem spacing

  the stems grow close together in compact clusters or tufts

  Stem thickness at base

  1–4 mm

Wetland status

Occurs only in non-wetlands. (Wetland indicator code: UPL)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae