couch grass vs witch grass

couch grass and witch grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
couch grass	Yes	No	No	No
witch grass	Yes	No	No	No

As nouns, couch grass and witch grass are synonyms defined as:

couch grass and witch grass: European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed

Other synonyms of couch grass include Agropyron repens, dog grass, quack grass, quackgrass, quick grass, witchgrass.

couch grass (noun)	witch grass (noun)
European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed	North American grass with slender brushy panicles; often a weed on cultivated land
	European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed