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Digitaria ischaemum — smooth crabgrass

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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)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf blade width
3–5 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
1.7–2.3 mm
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
Awn on glume
the glume has no awn
One or more florets
  • there is more than one floret per spikelet
  • there is one floret per spikelet
Lemma awn length
0 mm
Leaf ligule length
0.6–2.5 mm
Anther length
0.4–0.6 mm
Show all 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)

In New England

Distribution

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

Conservation status

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

Massachusetts
unranked (S-rank: SNR)

var. ischaemum

Massachusetts
unranked (S-rank: SNR)

From Flora Novae Angliae dichotomous key

3.  Digitaria ischaemum (Schreb.) Muhl. E

smooth crabgrass. Panicum ischaemum Schreb. • CT, MA, ME, NH, RI, VT. Roadsides, yards, railroads, lawns, sandy, disturbed soil.

Native to North America?

No

Sometimes confused with

Digitaria sanguinalis:
lower glume present and 0.2-0.4 mm long and upper lemma yellow to gray or brown (vs. D. ischaemum, with the lower glume absent or a tiny, membranous rim and upper lemma dark purple-brown).

Synonyms

  • Panicum ischaemum Schreb.

Family

Poaceae

Genus

Digitaria