horned poppy vs horn poppy

horned poppy and horn poppy both are nouns.

Word	Noun	Adjective	Verb	Adverb
horned poppy	Yes	No	No	No
horn poppy	Yes	No	No	No

As nouns, horned poppy and horn poppy are synonyms defined as:

horned poppy and horn poppy: yellow-flowered Eurasian glaucous herb naturalized in along sandy shores in eastern North America

Other synonyms of horned poppy include Glaucium flavum, sea poppy, yellow horned poppy.

horned poppy (noun)	horn poppy (noun)
yellow-flowered Eurasian glaucous herb naturalized in along sandy shores in eastern North America	yellow-flowered Eurasian glaucous herb naturalized in along sandy shores in eastern North America