witchgrass vs dog grass

witchgrass and dog grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
witchgrass	Yes	No	No	No
dog grass	Yes	No	No	No

As nouns, witchgrass and dog grass are synonyms defined as:

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

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

witchgrass (noun)	dog grass (noun)
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
European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed