groundcover vs undergrowth

groundcover and undergrowth both are nouns.

Word	Noun	Adjective	Verb	Adverb
groundcover	Yes	No	No	No
undergrowth	Yes	No	No	No

As nouns, undergrowth is a hypernym of groundcover; that is, undergrowth is a word with a broader meaning than groundcover:

groundcover: small plants other than saplings growing on a forest floor
undergrowth: the brush (small trees and bushes and ferns etc.) growing beneath taller trees in a wood or forest

Other hypernyms of groundcover include underbrush, underwood.

groundcover (noun)	undergrowth (noun)
small plants other than saplings growing on a forest floor	the brush (small trees and bushes and ferns etc.) growing beneath taller trees in a wood or forest
low-growing plants planted in deep shade or on a steep slope where turf is difficult to grow