piggyback plant vs youth-on-age

piggyback plant and youth-on-age both are nouns.

Word	Noun	Adjective	Verb	Adverb
piggyback plant	Yes	No	No	No
youth-on-age	Yes	No	No	No

As nouns, piggyback plant and youth-on-age are synonyms defined as:

piggyback plant and youth-on-age: vigorous perennial herb with flowers in erect racemes and having young plants develop at the junction of a leaf blade and the leafstalk

Other synonyms of piggyback plant include pickaback plant, Tolmiea menziesii.

piggyback plant (noun)	youth-on-age (noun)
vigorous perennial herb with flowers in erect racemes and having young plants develop at the junction of a leaf blade and the leafstalk	vigorous perennial herb with flowers in erect racemes and having young plants develop at the junction of a leaf blade and the leafstalk