screw tree vs shrub

screw tree and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
screw tree	Yes	No	No	No
shrub	Yes	No	No	No

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

Other hypernyms of screw tree include bush.

screw tree (noun)	shrub (noun)
a tree or shrub of the genus Helicteres	a low woody perennial plant usually having several major stems