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Sorghum halepense — Johnson grass

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Facts

Johnson grass is native to the Mediterranean, but is introduced worldwide and has become an important weed of warm temperate regions. The USDA considers it one of the six most damaging weeds in the United States, due to its destructive effects on crop yields and the difficulty of controlling it. Johnson grass can be found in most New England states except for Maine.

Habitat

Anthropogenic (man-made or disturbed habitats), 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
  • Vermont
Leaf blade width
8–40 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
3.6–6.5 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 one floret per spikelet
Lemma awn length
Up to 13 mm
Leaf sheath hair type
there are no hairs on the surface of the leaf sheath
Leaf ligule length
2–6 mm
Anther length
1.9–2.7 mm
Show all characteristics

  • Flowers

    Anther length
    1.9–2.7 mm
    Anther number
    3
    Awn on glume
    the glume has no awn
    Floret lower bract texture
    the lemma is thin and flexible
    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
    • 3
    • 5
    • 7 or more
    Inflorescence arrangement
    the plant has two types of spikelets with different reproductive structures
    Inflorescence axis orientation
    • the inflorescence axis is arched or curved outward
    • the inflorescence axis is straight
    Inflorescence branches
    the flowers are attached to branches rather than to the main axis of the inflorescence
    Inflorescence length
    100–500 mm
    Inflorescence type (general)
    the spikelets are borne on stalks or on branches
    Inflorescence type (specific)
    the inflorescence has pairs (or trios) of spikelets, but with one always either missing a stalk or on a shorter stalk than the other
    Lemma awn base
    the awn is attached right at the tip of the lemma
    Lemma awn length
    Up to 13 mm
    Lemma awn number
    • the lemma has no awn
    • the lemma has one awn on it
    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 split into two or more points
    Lemma vein number
    • 1
    • 3
    One or more florets
    there is one floret per spikelet
    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
    3.6–6.5 mm
    Spikelets spiny
    the spikelets do not appear spiny

  • Growth form

    Lifespan
    the plant lives more than two years
    Rhizomes
    yes
    Roots
    the plant has rhizomes (horizontal underground stem with roots growing from it)

  • Leaves

    Leaf auricles
    the leaves do not have auricles
    Leaf blade width
    8–40 mm
    Leaf ligule length
    2–6 mm
    Leaf ligule type
    the leaf ligule is in the form of a membrane with fine hairs
    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 no hairs on the surface of the leaf sheath
    Leaf sheath hairs
    there are no hairs on the surface of the leaf sheath

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Massachusetts
    • Vermont
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields

  • Stem, shoot, branch

    Stem orientation
    the stems are upright
    Stem spacing
    the stems grow singly or a few together (they may form diffuse colonies)

Wetland status

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

In New England

Distribution

Connecticut
present
Maine
absent
Massachusetts
present
New Hampshire
absent
Rhode Island
absent
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)

From Flora Novae Angliae dichotomous key

2.  Sorghum halepense (L.) Pers. E

Johnson grass. Holcus halepensis L. • CT, MA, VT; also reported from NH by Magee and Ahles (1999) and from RI by Seymour (1982), but specimens are unknown. Fields, disturbed soil, areas of cultivation.

Native to North America?

No

Sometimes confused with

Sorghastrum nutans:
pedicelled spikelet highly reduced, represented only by its pedicel, awns of sessile spikelet mostly 10-20 mm long, and anthers mostly 3-5 mm long (vs. S. halepense, with pedicelled spikelet of the pair diminutive but formed, awns of sessile spikelet 0-13 mm long, and anthers 1.9-2.7 mm long).
Sorghum bicolor:
plants annual or short-lived perennial, lacking rhizomes, leaf blades mostly 20–100 mm wide, and mature spikelets not or only tardily disarticulating (vs. S. halepense, with plants perennial, with rhizomes, leaf blades mostly 8–20 mm wide, and mature spikelets disarticulating).

Synonyms

  • Holcus halepensis L.

Family

Poaceae

Genus

Sorghum