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Digitaria filiformis — slender crabgrass

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Facts

Slender crabgrass is native to southern and eastern North America. In New England there are two varieties. One (Digitaria filiformis var. laeviglumis) is rare and endemic to New Hampshire, where it is found in peaty depressions on granite ledges. The other (D. filiformis var. filiformis) is a more widespread inhabitant of dry, open, sandy areas.

Habitat

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

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
  • wetlands
New England state
  • Connecticut
  • Massachusetts
  • New Hampshire
  • Rhode Island
Leaf blade width
1–6 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
1.3–2.8 mm
Glume relative length
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 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 no hairs on the surface of the leaf sheath
Leaf ligule length
0.3–1.5 mm
Anther length
0.3–0.6 mm
Show all characteristics

  • Flowers

    Anther length
    0.3–0.6 mm
    Anther number
    3
    Awn on glume
    the glume has no awn
    Bristles below spikelets
    no
    Floret lower bract texture
    the lemma is 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
    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
    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 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
    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
    1.3–2.8 mm
    Spikelet pedicel
    the spikelets have pedicels
    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
    1–6 mm
    Leaf ligule length
    0.3–1.5 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 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
    • wetlands
    New England state
    • Connecticut
    • Massachusetts
    • New Hampshire
    • Rhode Island
    Specific habitat
    • grasslands
    • man-made or disturbed habitats
    • meadows or fields
    • ridges or ledges

  • Stem, shoot, branch

    Roots at lower stem nodes
    • no
    • yes
    Stem orientation
    • the stems are upright
    • 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

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
unranked (S-rank: SNR)

var. filiformis

New Hampshire
historical (S-rank: SH), endangered (code: E)

var. laeviglumis

New Hampshire
historical (S-rank: SH), endangered (code: E)

From Flora Novae Angliae dichotomous key

2.  Digitaria filiformis (L.) Koel. NC

slender crabgrass. 2a. Digitaria laeviglumis Fern.; 2b. Panicum filiforme L. • CT, MA, NH, RI. Dry, open, often sandy, areas, such as fields, roadsides, and disturbed lots, also in peaty depression on granitic ledges. Digitaria filiformis resembles D. ischaemum and D. violescens in several character states, including the highly reduced lower glume, relative length of the upper glume, and color of the upper lemma. In addition to characters stated in the key, D. filiformis differs from the two mentioned species in its pustulose-based hairs on the lower sheaths 
(vs. glabrous to sparsely pubescent).

1a.  Lower lemmas glabrous … 2a. D. filiformis var. laeviglumis (Fern.) Wippf

1b.  Lower lemmas pubescent … 2b. D. filiformis var. filiformis

Variety laeviglumis is known from (and endemic to) NH. It is of regional conservation concern and occurs in peaty depressions on granitic ledges in Hillborough County. Variety filiformis is known from CT, MA, NH, RI.

Native to North America?

Yes

Sometimes confused with

Digitaria ischaemum

Family

Poaceae

Genus

Digitaria