• You are here:
• Dichotomous Key
• Poaceae
• Poaceae Group 10
• Digitaria
• Digitaria ischaemum

Digitaria ischaemum — smooth crabgrass

Facts

Smooth crabgrass is native to Eurasia and introduced in North America. It is a common weed of lawns but slighly less aggressive than hairy crabgrass (Digitaria sanguinalis).

Habitat

Anthropogenic (man-made or disturbed habitats)

Characteristics

• Flowers

  Anther length

  0.4–0.6 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

  1–2

  Floret types within spikelet

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

  Glume awn length

  0 mm

  Glume keel

  the glume keels are rough or hairy

  Glume relative length

  • both glumes are as long or longer than all of the florets
  • neither glume is quite as long as all of the florets

  Glume shape

  the glume is flat or curved in cross-section

  Glume veins

  • 0
  • 1
  • 3
  • 5
  • 7 or more

  Glumes per spikelet

  • 1
  • 2

  Inflorescence arrangement

  the spikelets are uniform

  Inflorescence axis orientation

  the inflorescence axis is straight

  Inflorescence branch length

  6–15.5 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 spread out, with clearly-evident branches

  Inflorescence type (general)

  the spikelets are borne on stalks or on branches

  Inflorescence type (specific)

  the inflorescence is branched and the branches all grow from the same side of the plant and look like spikes

  Inforescence position

  • the spikelets are mainly carried at the end of the stem
  • the spikelets are mainly found at the nodes, in the axils of leaves, along the stem

  Lemma awn base

  NA

  Lemma awn coiled

  NA

  Lemma awn length

  0 mm

  Lemma awn number

  the lemma has no awn

  Lemma awn orientation

  NA

  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 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

  • 1
  • 3
  • 5
  • 7 or more

  Lower glume length

  At least 0 mm

  Lower glume relative length

  the lower glume is one third or less as long as the upper glume

  One or more florets

  • there is more than one floret per spikelet
  • there is one floret per spikelet

  Palea length

  1.8–2.2 mm

  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 below the glumes

  Spikelet length

  1.7–2.3 mm

  Spikelet number per node

  0

  Spikelet pedicel

  the spikelets have pedicels

  Spikelet position

  the spikelets emerge from both the upper and lower halves of the inflorescence branches

  Spikelet shape

  • the spikelets are elliptic (widest in the middle, tapering to the ends) in profile
  • the spikelets are obovate (egg-shaped but with the widest point above the middle) in profile

  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

  1.3–2.3 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

  1.2–1.4 mm

• Growth form

  Horizontal rooting stem

  no

  Lifespan

  • the plant lives more than two years
  • the plant lives only a single year or less

  Rhizomes

  no

  Roots

  there are only slender roots on the plant

• Leaves

  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 hairy

  Leaf blade length

  1.5–9 cm

  Leaf blade width

  3–5 mm

  Leaf ligule length

  0.6–2.5 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 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
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  man-made or disturbed habitats

• Stem, shoot, branch

  Hairs at nodes

  the stem nodes are hairless or they have very sparse hairs

  Plant height

  20–70 cm

  Roots at lower stem nodes

  • no
  • yes

  Stem hairs

  the stem is nearly to completely hairless

  Stem node number

  3–4

  Stem orientation

  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

Usually occurs in non-wetlands, but occasionally in wetlands. (Wetland indicator code: FACU)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae