P&PDL Picture of the Week for
May 31, 2004

Ligules on Grass

Glenn Nice, Weed Diagnostician, Department of Botany & Plant Pathology, Purdue University

The ligule is defined as a projection at the base of the leaf blade in the grass family, by the Manual of the Vascular Flora of the Carolinas. It is a small membrane or fringe of hairs that extends up the stem of a grass from where the leaf blade separates from the sheath. This can be a membrane of different shapes and lengths, a fringe of hairs, or in some grasses absent. One thing that the ligule can do is aid in the identification of the grass. Below is a table of some of the ligules that can be found on some of Indiana’s common grasses.

The auricles are finger-like projections that can also be found where the leaf blade attaches to the stem. Whether these are present or not, or how they are shaped can also give clues as to which grass species you are looking at.

Ligule Auricles Species
Absent None

1. Barnyardgrass - Echinochloa crus-galli (Figure 1)

 

Fringe of hairs

None

1. Giant foxtail – Setaria faberi (1-3 mm)
  None 2. Green foxtailSetaria viridis (1-2 mm)
  None 3. Fall panicumPanicum dichotomiflorum (1-2.5 mm)
  None

4. WitchgrassPanicum capillare (1-1.5 mm)

 

Membranous

None

1. Annual bluegrassPoa annua (1-3 mm; truncate to sharply pointed)
Yes 2. Annual ryegrassLolium multiflorum (1-1.5 mm)
None 3. Downy bromeBromus tectorum (1-3 mm; rounded my be toothed)
None 4. JohnsongrassSorghum halepense (2-5 mm; truncate and appearing worn on margin)
None 5. Large crabgrassBromus sanquinalis (0.5-2 mm; truncate and jagged) (Figure 2)
None 6. OrchardgrassDactylis glomerata (2-8 mm; jagged to lacerate, rounded)
Yes 7. Perennial ryegrassLolium perenne (1-1.5 mm; toothed near the tip)
Yes 8. QuackgrassElymus repens (0.1-0.8 mm; truncate)
None 9. Reed canarygrassPhalaris arundinacea (2-6 mm; pointed to rounded, may be slightly toothed)
None 10. Shattercane - Sorghum biocolor (4-6 mm; ciliate along the edges, rounded or blunt)
None 11. Smooth crabgrassDigitaria ischaemum (0.6-2 mm; truncate, can have smooth margin)
None 12. Smooth bromeBromus inermis (0.5-2.5 mm; rounded, minutely jagged)
Yes

13. Tall fescueFestuca arundinacea (0.5 mm; truncate, jagged or toothed)

 

Membranous with fringe of hairs None 1. Yellow foxtail Setaria glauca (< 1mm) (Figure 3)

Sources:
A.E. Radford, H.E. Ahles, and C.R. Bell. 1968. Manual of the Vascular Flora of the Carolinas The University of North Carolina Press, Chapel Hill.

J. Stubbendieck, M. J. Coffin, and L.M. Landholt. 2003. Weeds of the Great Plains Nebraska Department of Agriculture, Bureau of Plant Industry, P.O. Box 94756. Lincoln, Nebraska 68509-4756

 

Click image to enlarge

Barnyardgrass

Barnyard grass

Large crabgrass

Large crabgrass

Yellow foxtail

Yellow foxtail

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service