vernal iris vs Iris verna

vernal iris and Iris verna both are nouns.

Word	Noun	Adjective	Verb	Adverb
vernal iris	Yes	No	No	No
Iris verna	Yes	No	No	No

As nouns, vernal iris and Iris verna are synonyms defined as:

vernal iris and Iris verna: low-growing spring-flowering American iris with bright blue-lilac flowers

Other synonyms of vernal iris include dwarf iris.

vernal iris (noun)	Iris verna (noun)
low-growing spring-flowering American iris with bright blue-lilac flowers	low-growing spring-flowering American iris with bright blue-lilac flowers