Many lawns are a mixture of both green (Cynodon dactylon) and blue (Digitaria didactyla) couch.
Colour can be an unreliable method of distinguishing between the two species, as this varies with seasonal conditions, fertiliser practices and elements causing plant stress.
Both couches have a spreading growth habit and a fine-to-medium texture.
The lighter-coloured tissue at the junction between the leaf blade and leaf sheath (known as the collar) is always free of hairs in both species. The leaf margins are not hairy and the average leaf width does not exceed 3 mm.
If you have a tufted grass, it is coarse-textured (>3 mm leaf width) or it has a hairy collar or leaf margin, it will be something other than green or blue couch.
The table below outlines the main points of difference between the two grasses.
Main points of difference between the blue and green couch grasses
|Point of difference||Green couch||Blue couch|
|Ligule (a small upright structure located on the inner side of a leaf between the leaf blade and leaf sheath)||A fringe of hairs||A continuous thin membrane|
|Presentation of emerging leaves||Folded, like the keel of a boat||Rolled|
Thanks to Desley Tree (DEEDI) for her assistance with the images of green and blue couch.