• You are here:
• Simple Key
• Grass-like plants
• True grasses
• Tridens flavus

Tridens flavus — purpletop tridens

Facts

Purpletop tridens is found in fields, roadsides and open woodlands. Although native to New England, some populations are introduced, such as those in Vermont railyards. This grass gets its name from the widely-spaced purple spikelets. After the grain ripens the upper branches become sticky.

Habitat

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

Characteristics

• Flowers

  Anther length

  1–1.5 mm

  Anther number

  At least 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

  4–8

  Floret types within spikelet

  there are at least two distinct forms of florets within one spikelet

  Glume awn length

  0 mm

  Glume relative length

  neither glume is quite as long as all of the florets

  Glume veins

  1

  Glumes per spikelet

  2

  Inflorescence arrangement

  the spikelets are uniform

  Inflorescence axis orientation

  the inflorescence axis is arched or curved outward

  Inflorescence branch length

  10–25 cm

  Inflorescence branches

  the flowers are attached to branches rather than to the main axis of the inflorescence

  Inflorescence branches coming off the lowest stem node

  1

  Inflorescence crowding

  the panicle is somewhat to very spread out, with clearly-evident branches

  Inflorescence length

  150–400 mm

  Inflorescence length to width ratio

  5–8

  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

  30–50 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 straight or twisted, but not coiled one half turn

  Lemma awn length

  0–0.5 mm

  Lemma awn number

  the lemma has more than 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 flat or rounded if you cut across the midpoint

  Lemma hairs

  the lemma has fine hairs between the veins

  Lemma keel hairs

  the keel of the lemma is rough, or has fine hairs

  Lemma marginal vein hairs

  the marginal vein of the lemma has fine hairs on it

  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

  3

  Lemma vein orientation

  the veins on the lemma stay roughly parallel throughout

  Lower glume length

  2.5–3 mm

  Lower glume relative length

  • the lower glume is nearly as long, or as long as, the upper glume
  • the lower glume is one third to three quarters as long as the upper glume

  One or more florets

  there is more than 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

  5–10 mm

  Spikelet number per node

  0

  Spikelet pedicel

  the spikelets have pedicels

  Spikelet pedicel length

  3–8 mm

  Spikelet position

  the spikelets emerge mainly from the upper halves of the inflorescence branches

  Spikelet shape

  the spikelets are ovate (egg-shaped, widest below the middle with rounded ends) in profile

  Spikelet width

  6–8 mm

  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

  3.5–4 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

  1.8–2 mm

• Growth form

  Horizontal rooting stem

  no

  Lifespan

  the plant lives more than two years

  Rhizomes

  yes

  Roots

  the plant has rhizomes (horizontal underground stem with roots growing from it)

• 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 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
  • the leaf blade is hairy

  Leaf blade length

  Up to 60 cm

  Leaf blade texture

  the leaf blade is smooth, or it may have soft hairs

  Leaf blade width

  3–10 mm

  Leaf ligule length

  Up to 0.5 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
  • Rhode Island
  • Vermont

  Specific habitat

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

• Stem, shoot, branch

  Hairs at nodes

  the stem nodes are hairless or they have very sparse hairs

  Plant height

  60–180 cm

  Roots at lower stem nodes

  no

  Stem hairs

  the stem is nearly to completely hairless

  Stem orientation

  the stems are upright

  Stem spacing

  the stems grow close together in compact clusters or tufts

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