sheep sorrel vs sour grass

sheep sorrel and sour grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
sheep sorrel	Yes	No	No	No
sour grass	Yes	No	No	No

As nouns, sour grass is a hypernym of sheep sorrel; that is, sour grass is a word with a broader meaning than sheep sorrel:

sheep sorrel: small plant having pleasantly acid-tasting arrow-shaped leaves; common in dry places
sour grass: any of certain coarse weedy plants with long taproots, sometimes used as table greens or in folk medicine

Other hypernyms of sheep sorrel include dock, sorrel.

sheep sorrel (noun)	sour grass (noun)
small plant having pleasantly acid-tasting arrow-shaped leaves; common in dry places	any of certain coarse weedy plants with long taproots, sometimes used as table greens or in folk medicine