tumble grass vs old witch grass

tumble grass and old witch grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
tumble grass	Yes	No	No	No
old witch grass	Yes	No	No	No

As nouns, tumble grass and old witch grass are synonyms defined as:

tumble grass and old witch grass: North American grass with slender brushy panicles; often a weed on cultivated land

Other synonyms of tumble grass include old witchgrass, Panicum capillare, witch grass, witchgrass.

tumble grass (noun)	old witch grass (noun)
North American grass with slender brushy panicles; often a weed on cultivated land	North American grass with slender brushy panicles; often a weed on cultivated land