Field guide to the identification of Cogongrass : with comparisons to other commonly found grass species in the southeast / C.W. Evans, D.J. Moorhead, C.T. Bargeron, and G.K. Douce

Field Guide to the Identification of
Cogongrass
With comparisons to other commonly found grass species in
the Southeast

Cogongrass (Imperata cylindrica) is an aggressive invader of natural and disturbed areas throughout the Southeast. It disrupts ecosystem functions, reduces wildlife habitat, decreases tree seedling growth and establishment success, and alters fire regimes and intensity. Recognizing the presence of cogongrass is necessary before beginning any management activities. While other species may look similar, cogongrass has a unique combination of characteristics that make field identification possible. This field guide describes and illustrates these characteristics and compares them to other grass species common found in similar habitats. Easy-to-understand terminology is used when possible, and definitions for technical terms are provided below. Cogongrass is a Federal Noxious Weed and any infestation must be identified by the appropriate state or federal authority. If you think you have cogongrass on your land, please contact your state department of agriculture or USDA-APHIS office. For more information of cogongrass ecology and control, visit www.cogongrass.org.
Scientific Names of Compared Species Vasey grass (Paspalum urvillei) Johnsongrass (Sorghum haplense) Silver beardgrass (Bothriochloa laguroides) Broomsedge (Andropogon virginicus)
Definitions Ligule - Small projection at the base of a leaf blade
Leaf sheath lower portion of the leaf which encloses the stem
Collar region junction of the leaf blade with the leaf sheath
Flower/Seed head entire group of flowers or seeds attached to
flower stalk
Rhizome Underground stem which often roots at nodes (often
thicker and more fleshy than roots)
Citation Evans, C.W., D.J. Moorhead, C.T. Bargeron, and G.K. Douce. 2008. Field Guide to the Identification of Cogongrass: With comparisons to other commonly found grass species in the Southeast. The University of Georgia Center for Invasive Species and Ecosystem Health, Tifton GA, BW-2008-02. 20 p.

Key Identification Features of Cogongrass
Flower/Seed head - Cylindrical in shape - 2-8 inches in length (total flower or
seed head) - Silvery white in color - Light fluffy dandelion-like seeds - Blooms from late March to mid June
(flower timing depends somewhat on local climate)
Leaves - Blades up to 6 feet long - About 1 inch wide - Whitish, prominent midrib, that is
often off center - Margins finely serrate - Some leaves are very erect, but some
may droop or lie flat - Often light yellowish-green in color - Could have a reddish cast in fall/
winter or brown after frost or freeze

C. Evans, UGA M. Atwater C. Evans, UGA

C. Evans, UGA T. Bodner, SWSS

J. Miller, USFS

Key Identification Features of Cogongrass
Plant Base - No apparent stem - Leaves appear to arise directly from
or close to the ground - Overlapping sheaths give a rounded
appearance to the plant base - All vegetation doesn't arise from one
dense clump, instead the plants are more spread out - Light-green to yellowish in color, or could be reddish - Often a lot of thatch around base
Leaf collar/Ligule - Ligule is a thin-fringed membrane - Leaf sheaths overlapping, giving the plant a round appearance - Hairy (the ligule is the most hairy part of the plant, the plant base may
also be somewhat hairy)

J. Miller, USFS

R. Carter, VSU

C. Evans, UGA

C. Evans, UGA

C. Evans, UGA

C. Evans, UGA

Key Identification Features of Cogongrass
Rhizome/Roots - Dense mat - Many sharp points - Covered in flaky scales - Bright white under scales - Strongly segmented
Rhizomes with scales removed (top) and intact (bottom)
Whole Plant - Densely growing patches - Tall grass (up to six feet, averaging 3-4 feet) - Circular infestations - Plants often turn brown in winter (at
least partially, but may depend on local climate)

J. Byrd, MSU

C. Evans, UGA

C. Bryson, USDA ARS J. Lotz, FDOACS

Cogongrass Infestation Identification

Forest - Flowering

Forest - Non-flowering

C. Evans, UGA C. Evans, UGA

C. Evans, UGA D. Moorhead, UGA

Forest - Dormant Season

Utility Rights-of-way

M. Atwater

Cogongrass Infestation Identification

C. Bryson, USDA ARS

Circular - Flowering

Circular - Non-flowering

J. Meeker, USFS

Open Area - Sparse Flowering

Open Area - Dense Flowering

J. Byrd, MSU

W. Faircloth, USDA ARS

C. Bryson, USDA ARS

Roadside - Flowering

Roadside - Non-flowering

G. Leach

Aerial View

Cogongrass - Flower and Seed Head Comparison
Flower/Seed head - Cylindrical in shape - 2-8 inches in length (total flower or
seed head) - Silvery white in color - Light fluffy dandelion like seeds - Blooms from late March to mid June
(flower timing depends somewhat on local climate)

C. Evans, UGA C. Evans, UGA

C. Evans, UGA

T. Bodner, SWSS J. Byrd, MSU

Vasey Grass
Flower/seed head not fluffy, but loosely branched and spreading

Silver Beardgrass
Very similar in looks, but often somewhat branched and blooms later in the year (June-August)

J. Miller, USFS J. Miller, USFS

Broomsedge
Flower/seed head is thin and sparsely flowered, blooms late
summer

Johnsongrass
Flower/seed head not-fluffy, but loosely branched and spreading

C. Evans, UGA C. Evans, UGA

Cogongrass - Leaf Collar and Ligule Comparison
Leaf collar/Ligule - Ligule is a thin-fringed membrane - Leaf sheaths overlapping, giving the plant a round appearance - Hairy (the ligule is the most hairy part of the plant, the plant base may
also be somewhat hairy)

C. Evans, UGA

J. Byrd, MSU

C. Evans, UGA J. Byrd, MSU

Vasey Grass
Only membranous ligule is hairy, leaf collar flared, giving the region
a less rounded look

Silver Beardgrass
Collar region hairless except for ligule, which has sparse long hairs.

C. Evans, UGA

D. Moorhead, UGA

C. Evans, UGA

D. Moorhead, UGA

Broomsedge
Sheath is somewhat hairy, ligule is covered in numerous long thin hairs

Johnsongrass
Smooth collar, not hairy except for a small white hair-patch behind ligule

C. Evans, UGA

Cogongrass - Leaf Comparison
Leaves - Blades up to 6 feet long - About 1 inch wide - Whitish, prominent midrib, that is
often off center - Margins finely serrate - Some leaves are very erect, but some
may droop or lie flat - Often light yellowish-green in color - Could have a reddish cast in fall/
winter or brown after frost or freeze

T. Bodner, SWSS

J. Byrd, MSU

C. Evans, UGA

Vasey Grass
Leaves arise from apparent stem, and serrations are not as obvious

Silver Beardgrass
Leaves are not serrated and arise from an apparent stem. Midrib not
as apparent

C. Evans, UGA

D. Moorhead, UGA

D. Moorhead, UGA

T. Bodner, SWSS

J. Miller, USFS D. Moorhead, UGA

Broomsedge
Leaves are thin and often curled, and arise from apparent stem

Johnsongrass
Leaves wider than cogongrass, edges are not serrate

R. Carter, VSU

Cogongrass - Plant Base Comparison
Plant Base - No apparent stem - Leaves appear to arise directly from
or close to the ground - Overlapping sheaths give a rounded
appearance to the plant base - All vegetation doesn't arise from one
dense clump, instead the plants are more spread out - Light-green to yellowish in color, or could be reddish - Often a lot of thatch around base

J. Miller, USFS

J. Miller, USFS

C. Evans, UGA

C. Evans, UGA C. Evans, UGA

Vasey Grass
Base thick and flattened, often with a reddish-purple color. Plant is very bunched in appearance.

Silver Beardgrass
Plant base has a strongly bunched appearance, with apparent stems

D. Moorhead, UGA C. Evans, UGA

Broomsedge
Plant base has a strongly bunched appearance, with very apparent
stems

Johnsongrass
Plant base also rounded, but very thick in comparison to cogongrass.
Plant does not appear bunched.

C. Evans, UGA

Cogongrass - Rhizome and Root Comparison
Rhizome/Roots - Dense mat - Many sharp points - Covered in flaky scales - Bright white under scales - Strongly segmented

J. Byrd, MSU

C. Evans, UGA

C. Evans, UGA

C. Evans, UGA

C. Evans, UGA

Vasey Grass
Thin root system, not extensive and lacking thick, segmented rhizomes

Silver Beardgrass
Root system fibrous, lacking rhizomes

S. Dewey, USU

S. Dewey, USU

D. Moorhead, UGA

Broomsedge
Root system fibrous, lacking rhizomes

Johnsongrass
Rhizome system not as extensive. Rhizomes lacking scaly coverings.

C. Bryson, USDA ARS

Cogongrass - Whole Plant Comparison
Whole Plant - Densely growing patches - Tall grass (up to six feet, averaging
3-4 feet) - Circular infestations - Plants often turn brown in winter (at
least partially, but may depend on local climate)

J. Lotz, FDOACS

Johnsongrass

Broomsedge

J. Miller, USFS T. Bodner, SWSS

Silver Beardgrass

Vasey Grass

T. Bodner, SWSS C. Bryson, USDA ARS