tumble grass vs old witchgrass

tumble grass and old witchgrass both are nouns.

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

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

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

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

tumble grass (noun)	old witchgrass (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