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Digitaria cognata — fall crabgrass

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Facts

Fall crabgrass is native to New England, but has expanded its range in our region due to its affinity for human-disturbed habitats. It prefers open, dry, sandy sites. The seeds of this grass are edible, and were traditionally eaten by the Hopis in Arizona.

Habitat

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

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
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf blade width
2–5.4 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
2.2–3.1 mm
Glume relative length
one or both glumes are as long or longer than 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 sheath hair type
  • there are hairs on the surface of the leaf sheath, and some of the hairs have blisters at their bases
  • 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 ligule length
0.2–1.5 mm
Anther length
0.5–0.7 mm
Show all characteristics

  • Flowers

    Anther length
    0.5–0.7 mm
    Anther number
    3
    Awn on glume
    the glume has no awn
    Bristles below spikelets
    no
    Floret lower bract texture
    the lemma is hard and firm
    Floret number
    1–2
    Floret types within spikelet
    • NA
    • there are at least two distinct forms of florets within one spikelet
    Glume relative length
    one or both glumes are as long or longer than all of the florets
    Glume shape
    the glume is flat or curved in cross-section
    Glume veins
    • 0
    • 1
    • 3
    • 5
    • 7 or more
    Inflorescence arrangement
    the spikelets are uniform
    Inflorescence axis orientation
    the inflorescence axis is straight
    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 length
    128–275 mm
    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
    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 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
    One or more florets
    • there is more than one floret per spikelet
    • there is one floret per spikelet
    Palea relative length
    palea is one half to fully as long as lemma
    Spikelet axis tip
    there is no extension of the spikelet axis beyond the tip of the spikelet
    Spikelet length
    2.2–3.1 mm
    Spikelet pedicel
    the spikelets have pedicels
    Spikelet pedicel length
    10–40 mm
    Spikelets spiny
    the spikelets do not appear spiny
    Upper glume shape
    the upper glume is widest at or below the middle

  • Leaves

    Leaf auricles
    the leaves do not have auricles
    Leaf blade width
    2–5.4 mm
    Leaf ligule length
    0.2–1.5 mm
    Leaf ligule type
    the leaf ligule is in the form of a membrane
    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, and some of the hairs have blisters at their bases
    • 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
    • grasslands
    • man-made or disturbed habitats
    • meadows or fields

  • Stem, shoot, branch

    Stem spacing
    the stems grow close together in compact clusters or tufts

Wetland status

Not classified

In New England

Distribution

Connecticut
present
Maine
absent
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
not applicable (S-rank: SNA)
New Hampshire
unrankable (S-rank: SU), Ind (code: Ind)

From Flora Novae Angliae dichotomous key

1.  Digitaria cognata (J.A. Schultes) Pilger N

Fall crabgrass. Leptoloma cognatum (J.A. Schultes) Chase • CT, MA, NH, RI, VT. Sandy fields, roadsides, railroads, grasslands, and other open, dry, sandy areas. Thought by Sorrie and Somers (1999) to be introduced; however, this species, like others it resembles (e.g., Eragrostis spectabilis, Panicum capillare), is capable of using human-disturbed habitats and has expanded its range in New England as a result. See Zika (1990) for discussion of this grass in VT.

Native to North America?

Yes

Sometimes confused with

Panicum capillare:
plants annual, panicles 7-24 cm wide, and upper lemmas indurate and lustrous, firm and slightly revolute at the margin (vs. D. cognata, with plants perennial, panicles 16.5-44.5 cm wide, the upper lemma not rigidly indurate, hyaline and flat at the margin).
Panicum philadelphicum:
plants annual, panicles 4-24 cm wide, and upper lemmas indurate and lustrous, firm and slightly revolute at the margin (vs. D. cognata, with plants perennial, panicles 16.5-44.5 cm wide, the upper lemma not rigidly indurate, hyaline and flat at the margin).

Synonyms

  • Leptoloma cognatum (J.A. Schultes) Chase

Family

Poaceae

Genus

Digitaria