silversword vs shrub

silversword and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
silversword	Yes	No	No	No
shrub	Yes	No	No	No

As nouns, shrub is a hypernym of silversword; that is, shrub is a word with a broader meaning than silversword:

silversword: low-growing plant found only in volcanic craters on Hawaii having rosettes of narrow pointed silver-green leaves and clusters of profuse red-purple flowers on a tall stem
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of silversword include bush.

silversword (noun)	shrub (noun)
low-growing plant found only in volcanic craters on Hawaii having rosettes of narrow pointed silver-green leaves and clusters of profuse red-purple flowers on a tall stem	a low woody perennial plant usually having several major stems